ArcadeVGA Trinitron half screen issues

[jaf]

Hi all,

I've hooked up Ultimarc's ArcadeVGA with a Sony 25" trinitron TV via Scart RGB. 

After installation of the ArcadeVGA Catalyst software all looks good;  I select the 15-31 monitor on the Trisync utility and the QuickRes tool works with most low-res options for the classic games.  However,  the default 640x480 causes he TV to have a double image left/right and the 800x600 is out of synch.  After looking at the settings for each of the resolution using Powerstrip, I see they're not set to interlaced.   Once I've set them to interlaced the screen display shows but now I only see top half of the Windows XP desktop.  This would make me think the TV can't support a vertical res of 480+, but the resolution 512x512 works fine as too does 1024x768 with slight panning.  The 1024x768 is actually 800x600 with a 1024x768 desktop;  again the image looks fine.  I also tried setting the Trisync back to the standard 15hHz to no avail.

So, why can't I get 640x480 working?  I'm convinced the vga->scartrgb is correct as it wouldn't show the other resolutions.

Any suggestions would be most helpful.