VGA or monitor problem?

[jankohrasko]

The problem is that sometimes monitor goes black and back and black and back again very quickly (maybe 20 times in minute) and it's impossible to work with it. Monitor is plugged via DVI cable.
But when I connected monitor to other PC - it works fine. When I connected a different monitor to that "problematic" PC it works fine again.
I have this same problem with two different PC, both of them have Asus ATI9600XT VGA cards and both of them use LCD monitor made by Philips (but 2 different types). And both PCs run Win XP, were working fine for a few months, and the problem isn't there always - just sometimes. They are at different places, in different parts of town.
What would you recommend to do?

[flanzig1]

What refresh rate and resolution are you running on the LCD? LCDs should be run at a 60hz refresh and the resolution at native. Each size LCD has a different native resolution.

[jankohrasko]

I don't remember the resolution right now, but the one I've checked yesterday had refresh rate set to 75Hz and I have set it down to 70Hz. Is it too much? But why it worked fine for months with the same parameters set?

[glc]

For best results, you need to use 60Hz or 75Hz refresh rate on a LCD. If 75 causes issues, drop it to 60, don't use 70.

[jankohrasko]

OK, I'll try. Thanks.