need some clarification

[mahalos]

hey guys,

i need some clarification!!!!  i'm currently running a Nanao 26" (15khz) with an Arcadevga and a Jpac. I'm having problems with my monitor whilst running 640x480, i need to know that "technically" there shouldn't be any problems running this resolution.

[menace]

640x480 is an interlaced resolution and some monitors just won't run that.  Without more info as to what you are doing thats about all I can comment.

[Harry Potter]

A wild guess: Is your picture rolling? 

[mahalos]

i have the dual resolution nanao and it has always been on low(15khz).
I always run my frontend (mamewah) at 640x288 and it's mint, but my desktop runs at 640x480 and it's fine and stable when i first turn the machine on, but after about 15-20mins on that resolution, the image starts violently shaking/jumping.....not rolling! and it can't be stopped with the v-hold pot. If i click back into mamewah it's fine????exit back out again and it's jumping jack city.
it's been doing this for as long as i can remember, and i've gotten around the problem by remote administering. The problem i have now is i've installed Zinc as another emulator and the games are supposed to run at 640x480, and i've also loaded up house of the dead 2 and 3 to play with my light gun but they also use the same resolution.....so i only get to play these games for about fifteen minutes before it craps out.
i just needed to now that it's a monitor problem rather than anything else.