Okay, I've been playing with advancemame/menu for a few days now and have got nowhere..... Time to ask the experts

Details :
Gentoo Linux 2.6.7
svgalib 1.9.19
advmame/menu - latest versions as far as I know
AMD 350MHz (slowish hence wanting to use svgalib !)
HP Ultra VGA 1280 17" monitor
nvidia geforce 64mb agp
When I try advmame, advmenu or advcfg all I get is a black screen. advcfg goes through the setup screens okay its when it tries to display the "test" screens that it goes black/blank.
I've set the horizontal and vertical clock speeds as per the monitors manual in /etc/vga/libvga.conf as follows ;
HorizSync 30 69
VertRefresh 50 160
I then added these values to advmame.rc along with the pclock setting of 5-110 (the 110 comes from the monoitors manual). Not sure why but I have to include a range and advcfg recommends strating at 5.
I'm begining to think the pclock setting is wrong for my monitor (just a guess though).
Just to confuse the issue, I decided to see what happens if I run advmame/menu in X (running xfce4) and it works !!!! Why is this ? Unfortunetely, too many games are too slow under X so its not an option.
If I run xmame.svga <game> then the game works (and a lot faster than under X) so I'm assuming that my svgalib settings are all correct.
Anyone following me so far ? I'm really stuck here and would appreciate any help given. I've tried changing the pclock range and re-running advmame and the only difference i get is some games report that there is no video mode available. On one occasion I did get some random lines and colours on the screen but I had to reboot to get rid of them (probably not a good idea to mess with them then

).
Any help appreciated.
Many thanks for listening,
Buks