Hmm.... I have heard this mentioned a lot, but have yet to ever see it happen.
I'm using a Voodoo 5 5500, and leave it on for days on end... longest running time about 96 hours non stop fish (yeah, four days)
But from experience, I would check your drivers first. And remember, newest doesn't mean best. Sometimes you need to downgrade to a better driver.
Second, check and see if your video card has been overclocked. If you don't know how to check for that, search for overclocking your video card type, on
www.google.com and you will find instructions on how to do it, and even how to "underclock".
Overclocking can overheat the video card (and too much overclocking can in some cases damage the card)
Underclocking will make it run cooler, and prevent some lock ups.
Just remembered one more tip, onr that just might fix your problem.
Right click the "MY COMPUTER" icon, and select "PROPERTIES".
Click the "PERFORMANCE" tab (with WIN 98, not sure about WIN ME or XP)
Click on "GRAPHICS" and adjust the slider down one notch. It is probably maxed out, and dropping it one notch sometimes makes a BIG difference.
Hope this helps.