first of all thank to everyone here at the forum and to all the developers of this great emulator.
But now here's my problem:
recently I bought a new laptop equipped with windows 7 (home premium) and a new graphic card (radeon 6490m) to be put inside my arcade cabinet. The cabinet has a 640x480 crt and I use the VGA out of the laptop to get the output.
Now, I'm using ZSnes 1.51 and when I set any 640x480 full screen resolution, the image get messed up (as in the picture).

After this, if I do not touch anything, the emulator get back to last (working) resolution.
Can someone please give me some advice?
Thank you!!!