I've uploaded a new test version (groovymame32_0142.012o_test.rar), this one should finally fix the galaxian and scramble issues, at least at first sight, don't know if there are more hidden side effects or other games related to these that still have issues.
Nvidia card drivers afford the ability for custom resolutions, that I think goes beyond the '32 mode limit', which may be one reason AdvMAME works with them. Have you explored this?
The 32 mode limit for nVidia cards is not something that I've tested myself, but that read in the great documentation on different video cards made by Sailorsat for the German site.
Indeed, I've got an nVidia in this laptop and have defined about 100 modes using Powerstrip, that after all has to use the driver resources to make them available, so it seems likely that the driver itself let us define that amount of modes. But... the problem is that, like with Ati cards, there are two registry keys used for defining a video mode, first one is just the xres,yres,vfreq thing, second one is where you actually define the custom timings. The problem is that the driver can't read more than 32 of these second registry keys, so you can have many video modes but probably can't define a custom timing for more than 32 of them...