I upgraded to 6.6, but it still gives me the same problem with DVDs.
It says "burn process failed at 4x"
I don't have any DVD players installed, so the drivers should be fine.  It says it's using the nero aspi driver.
I was trying to burn a DVD video from a vob/ifo set I created. (unencrypted)
Here is my log:
Windows XP 5.1
IA32
WinAspi: File 'Wnaspi32.dll': Ver=4.71 (0002), size=45056 bytes, created 7/17/2002 9:03:20 AM 
ahead WinASPI: File 'C:\Program Files\Nero6\Nero\Wnaspi32.dll': Ver=2.0.1.74, size=164112 bytes, created 10/26/2004 4:21:30 PM 
Nero Version: 6.6.0.6
Recorder:             <PLEXTOR DVDR   PX-708A>  Version: 1.08 - HA 1 TA 3 - 6.6.0.6
 Adapter driver:      <nvatabus>                HA 1
 Drive buffer  :      2048kB
 Bus Type      :      default (0) -> ATAPI, detected: ?
CD-ROM:               <CREATIVE  CD5233E        >Version: 2.05 - HA 1 TA 2 - 6.6.0.6
 Adapter driver:      <nvatabus>                HA 1
=== Scsi-Device-Map ===
DiskPeripheral       : ST3120022A              3.06   iteraid Port 0 ID 0  DMA: Off
DiskPeripheral       : WDC WD800LB-00DMA1      17.0   iteraid Port 0 ID 1  DMA: Off
DiskPeripheral       : ST3120022A                    nvatabus Port 1 ID 0  DMA: Off
DiskPeripheral       : ST3160023A                    nvatabus Port 1 ID 1  DMA: Off
CdRomPeripheral      : CREATIVE  CD5233E             nvatabus Port 1 ID 2  DMA: Off
CdRomPeripheral      : PLEXTOR DVDR   PX-708A        nvatabus Port 1 ID 3  DMA: Off
DiskPeripheral       : HDS722525VLSA80         V36O    SI3112 Port 2 ID 0  DMA: Off
CdRomPeripheral      : AXV     CD/DVD-ROM      2.0B    axsaki Port 3 ID 0  DMA: Off
=== CDRom-Device-Map ===
CREATIVE CD5233E           X:   CDRom0
PLEXTOR DVDR   PX-708A     G:   CDRom1
AXV CD/DVD-ROM             L:   CDRom2
=======================
AutoRun : 1
Excluded drive IDs: 
WriteBufferSize: 83886080 (83886080) Byte
ShowDrvBufStat : 0
BUFE           : 0
Physical memory     : 1023MB (1048048kB)
Free physical memory: 597MB (612108kB)
Memory in use       : 41 %
Uncached PFiles: 0x0
Use Inquiry    : 1
Global Bus Type: default (0)
Check supported media : Disabled (0) 
20.1.2005
UDF/ISO compilation
5:52:36 AM   #1 Phase 112 File dlgbrnst.cpp, Line 1832
   DVD-Video files reallocation started
   
5:52:36 AM   #2 Text 0 File DVDVideoCompilation.cpp, Line 549
   Content of VIDEO_TS.IFO has been modified
   
5:52:36 AM   #3 Text 0 File DVDVideoCompilation.cpp, Line 549
   Content of VIDEO_TS.BUP has been modified
   
5:52:36 AM   #4 Text 0 File DVDVideoCompilation.cpp, Line 549
   Content of VTS_01_0.IFO has been modified
   
5:52:36 AM   #5 Text 0 File DVDVideoCompilation.cpp, Line 549
   Content of VTS_01_0.BUP has been modified
   
5:52:36 AM   #6 Text 0 File DVDVideoCompilation.cpp, Line 549
   Content of VTS_02_0.IFO has been modified
   
5:52:36 AM   #7 Text 0 File DVDVideoCompilation.cpp, Line 549
   Content of VTS_02_0.BUP has been modified
   
5:52:36 AM   #8 Phase 113 File dlgbrnst.cpp, Line 1832
   DVD-Video files reallocation completed
   
5:52:36 AM   #9 Text 0 File Isodoc.cpp, Line 6168
   Iso document burn settings
   ------------------------------------------
   Determine maximum speed : FALSE
   Simulate                : FALSE
   Write                   : TRUE
   Finalize CD             : TRUE
   Multisession            : FALSE
   Burning mode            : DAO
   Mode                    : 1
   ISO Level               : 1 (Max. of 11 = 8 + 3 char)
   Character set           : ISO 9660
   Joliet                  :FALSE
   Allow pathdepth more than 8 directories : FALSE
   Allow more than 255 characters in path  : FALSE
   Write ISO9660 ;1 file extensions        : TRUE
   
5:52:36 AM   #10 Phase 111 File dlgbrnst.cpp, Line 1832
   DVD-Video files sorted
   
5:52:36 AM   #11 Text 0 File Reader.cpp, Line 127
   Reader running
   
5:52:36 AM   #12 Text 0 File Writer.cpp, Line 122
   Writer PLEXTOR  DVDR   PX-708A   running
   
5:52:36 AM   #13 ISO9660GEN -11 File geniso.cpp, Line 3286
   First writeable address = 0 (0x00000000)
   
5:52:36 AM   #14 ISO9660GEN -11 File geniso.cpp, Line 3286
   First writeable address = 0 (0x00000000)
   
5:52:36 AM   #15 Text 0 File Burncd.cpp, Line 3155
   Turn on Disc-at-once, using DVD media
   
5:52:36 AM   #16 Text 0 File DlgWaitCD.cpp, Line 257
   Last possible write address on media:  2295103 (510:01.28, 4482MB)
   Last address to be written:            2105551 (467:54.01, 4112MB)
   
5:52:36 AM   #17 Text 0 File DlgWaitCD.cpp, Line 269
   Write in overburning mode: NO
   
5:52:36 AM   #18 Text 0 File DlgWaitCD.cpp, Line 2311
   Recorder: PLEXTOR DVDR   PX-708A, Media type: DVD+RW
    Disc Manufacturer ID: MKM, Media Type ID: A02, Product revision number: 0
    Disc Application Code: 0, Extended Information Indicators: 1
   
5:52:36 AM   #19 Text 0 File DlgWaitCD.cpp, Line 431
   >>> Protocol of DlgWaitCD activities: <<<
   =========================================
   
5:52:36 AM   #20 Text 0 File ThreadedTransferInterface.cpp, Line 829
   Setup items (after recorder preparation)
    0: TRM_DATA_MODE1 ()
       2 indices, index0 (150) not provided
       original disc pos #0 + 2105552 (2105552) = #2105552/467:54.2
       relocatable, disc pos for caching/writing not required/ required, no patch infos
       -> TRM_DATA_MODE1, 2048, config 0, wanted index0 0 blocks, length 2105552 blocks [PLEXTOR  DVDR   PX-708A]
   --------------------------------------------------------------
   
5:52:36 AM   #21 Text 0 File ThreadedTransferInterface.cpp, Line 1042
   Prepare recorder [PLEXTOR  DVDR   PX-708A] for write in CUE-sheet-DAO
   DAO infos:
   ==========
    MCN: ""
    TOCType: 0x00; Session Closed, disc fixated
    Tracks 1 to 1:
      1: TRM_DATA_MODE1, 2048/0x00, FilePos             0             0    4312170496, ISRC ""
   DAO layout:
   ===========
    __Start_|____Track_|_Idx_|_CtrlAdr_|_RecDep__________
          0 |  lead-in |   0 |    0x41 | 0x00
          0 |        1 |   0 |    0x41 | 0x00
          0 |        1 |   1 |    0x41 | 0x00
    2105552 | lead-out |   1 |    0x41 | 0x00
   
5:52:36 AM   #22 Phase 24 File dlgbrnst.cpp, Line 1832
   Caching of files started
   
5:52:36 AM   #23 Text 0 File Burncd.cpp, Line 4042
   Cache writing successful.
   
5:52:36 AM   #24 Phase 25 File dlgbrnst.cpp, Line 1832
   Caching of files completed
   
5:52:36 AM   #25 Phase 36 File dlgbrnst.cpp, Line 1832
   Burn process started at 4x (5,540 KB/s)
   
5:52:36 AM   #26 Text 0 File ThreadedTransferInterface.cpp, Line 2604
   Verifying disc position of item 0 (relocatable, disc pos, no patch infos, orig at #0): write at #0
   
5:52:36 AM   #27 Text 0 File Cdrdrv.cpp, Line 8332
   ---- DVD Structure: Physical Format Information (00h) ----
   Layer: 0, Address: 0 (0 h), AGID: 0; Length: 2050
    Book Type: DVD+RW  (9), Part Version: 2
    Disc Size: 120 mm,      Maximum Rate: <not specified> (F h)
    Number of Layers: 1,    Track Path: Parallel Track Path (PTP),  Layer Type: re-writable
    Linear Density:         0,267 um/bit,  Track Density:  0,74 um/track
    Starting Physical Sector Number of Data Area: 30000 h (DVD-ROM, DVD-R/-RW, DVD+R/+RW)
    End Physical Sector Number of Data Area:      9800F h
    End Sector Number in Layer 0:                 0 h
    Data in Burst Cutting Area (BCA) does not exist
     Disc Application Code: 0 / 0 h
     Extended Information indicators: 1 h
     Disc Manufacturer ID: MKM.....
     Media type ID: A02
     Product revision number: 0
     Number of Physical format information bytes in use in ADIP up to byte 63: 57
    Media Specific [16..63]:
         00 00 01 4D 4B 4D 00 00 - 00 00 00 41 30 32 00 39    ...MKM.....A02.9
         23 00 94 79 64 02 20 00 - 9C 7A 6C 02 20 00 9A 7B    #..yd....zl....{
         68 02 20 12 12 10 E0 00 - F0 00 00 00 00 00 00 00    h...............
   
5:52:36 AM   #28 Text 0 File DVDPlusRW.cpp, Line 615
   Start write address at LBA 0
   DVD high compatibility mode: Yes
   
5:57:09 AM   #29 SCSI -1135 File Cdrdrv.cpp, Line 1432
   SCSI Exec, HA 1, TA 3, LUN 0, buffer 0x03E80000
   Status:     0x04 (0x01, SCSI_ERR)
   HA-Status   0x00 (0x00, OK)
   TA-Status   0x02 (0x01, SCSI_TASTATUS_CHKCOND)
   Sense Key:  0x03 (KEY_MEDIUM_ERROR)
   Sense Code: 0x0C
   Sense Qual: 0x00
   CDB Data:   0x2A 0x00 0x00 0x0B 0x38 0x40 0x00 0x00 0x20 0x00 0x00 0x00 
   Sense Data: 0xF0 0x00 0x03 0x00 0x0E 0x38 0x40 0x0A 
               0x00 0x00 0x00 0x00 0x0C 0x00 
   
5:57:09 AM   #30 CDR -1135 File Writer.cpp, Line 311
   Write error
   
5:57:09 AM   #31 Text 0 File ThreadedTransfer.cpp, Line 228
   all writers idle, stopping conversion
   
5:57:09 AM   #32 Text 0 File ThreadedTransfer.cpp, Line 222
   conversion idle, stopping reader
   
5:57:09 AM   #33 Text 0 File DVDPlusRW.cpp, Line 833
   Media-Format will be stopped after burning
   
5:57:09 AM   #34 Phase 127 File dlgbrnst.cpp, Line 1832
   Generating DVD high compatibility borders
   
5:57:22 AM   #35 Phase 38 File dlgbrnst.cpp, Line 1832
   Burn process failed at 4x (5,540 KB/s)
   
Existing drivers:
File 'Drivers\CDRALW2K.SYS': Ver=6.1.1.7 , size=24698 bytes, created 6/24/2003 11:18:48 PM 
File 'Drivers\ASPI32.SYS': Ver=4.71 (0002) built by: WinDDK, size=16512 bytes, created 7/17/2002 8:05:10 AM 
File 'Drivers\nvatabus.sys': Ver=5.10.2600.0446 built by: WinDDK, size=79360 bytes, created 6/3/2004 10:40:46 AM (Adapter driver for rec)
Registry Keys:
HKLM\Software\Microsoft\Windows NT\CurrentVersion\WinLogon\AllocateCDROMs : 0 (Security Option)