Recently, like in the last month or so, a couple of my computers have started having a problem with random screen flashing: suddenly, the screen just flashes as though it were refreshing or changing the wallpaper or ... but, nothing has changed. Sometimes the video gets "stuck" if I'm in a graphics app, and I have to minimize and then restore whatever application I'm using in order to get the graphics to straighten out. For example, I'll be playing Spider Solitaire. After the screen has flashed a few times, the cards will start acting strangely: I just moved one, but it'll seem to still be where it was. When I minimize and restore the app, then the cards are where they're supposed to be - until the screen has flashed a few more times. And the flashing is pretty consistent - it's not like once a day or something - it's more like a few times per hour (though I haven't timed it exactly - hmm).
This is happening on two HP's and an eMachine (Gateway), all running Windows XP service pack 2. I've got a Mactel running XP and another HP - neither of which have the problem.
There is anti-virus and anti-spyware software running on all the machines. They all receive regular Windows updates. I updated the video drivers on the eMachine and one of the HPs with no effect.
A couple of friends who have purchased Vista recently are complaining about the same thing - one of them even took their new PC back to the store and exchanged it, thinking something was wrong with the video.
Anybody have a clue as to what's going on here?