Hi tiobolinha,
In order to find out what's happening, please try the following:
1) Download the latest VMMaker/Arcade_OSD versions, from Krick's mirror site:
http://mame.3feetunder.com/windows-ati-crt-emudriver/2) Edit vmmaker.ini, set
MonitorType = "CUSTOM" and the following line:
monitor_specs_0 15625-15800, 49.50-65.00, 2.000, 4.700, 8.000, 0.064, 0.160, 1.056, 0, 0, 200, 4483) Still in vmmaker.ini, set your GroovyMAME's path
4) Run VMMaker, restart (make sure your desktop is set to 640x480@60 before restarting)
5) Once in Windows, adjust your monitor if necessary to get a proper picture at 640x480. Notice it will be interlaced (flicker), that's fine.
6) Launch Arcade_OSD. Now, start testing resolutions, from the lower to the higher ones. ONLY test the ones marked as CUSTOM!! Notice which ones work, which ones don't. Try to find a logic. Probably the lower ones don't work, but the higher ones do. That would be a problem with low dotclocks. Report back.
7) If you can't find any logic, post your Modeline.txt file (inside your VMMaker folder) and mark a few of them that work, a few that don't (don't need to test them all).