I haven't really had much experiance with it yet but I know it has to do with the list_generation_method.  You need it to compare your rom files with the known list of available games.  It works for me when I use the default list_generation_method for mame of rom_folder_vs_listxml.  Here is a copy of my mame.ini:
### mame.ini (mamewah v1.62) ###
emulator_title                            MAME
### List Generation Settings ###
rom_path                                  C:\Emulation\Mame32\roms
rom_extension                             zip
dat_file                                  auto:[emuexepath]\[emuexename].dat
nms_file                                  auto:[emuexepath]\[emuexename].nms
catver_ini_file                           auto:[emuexepath]\catver.ini
list_generation_method                    rom_folder_vs_listxml
### Execution Settings ###
pre_emulator_app_commandlines             
emulator_commandline                      C:\Emulation\Mame32\mame32.exe "[rompath]\[name].[romext]"
post_emulator_app_commandlines            
general_app_commandlines                  
### Artwork Settings ###
artwork_image_paths                       auto:[emuexepath]\snap;[emuexepath]\titles;[emuexepath]\marquee;
[emuexepath]\control;[emuexepath]\cabinet;[emuexepath]\flyers;[emuexepath]\boxart;
[emuexepath]\cart;[emuexepath]\art9;[emuexepath]\art10
movie_preview_path                        auto:[emuexepath]\previews
movie_artwork_no                          1
enable_fuzzy_search                       0
history_dat_file                          auto
history_dat_artwork_no                    2
### Screen-Saver Settings ###
enable_music_in_screensaver               1
select_random_game                        0
saver_type                                gamelist_slideshow
movie_path                                
movie_fullscreen                          1
quit_delay                                0
saver_commandline                         
### Additional Settings ###
music_path                                
lcd_display_file_path                     
description_display                       [description]{scroll}
### Settings used by MAMEWAH ###
current_list                              0
Don't know if it'll help, but hopefully.
Later,
Brian