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I've had this problem for awhile now, and I just haven't much cared about it until now, when I'm quite sick of it.
I'm on Windows XP and I have an ATI Radeon X300/X550/X1050 Series video card (not sure why the numbers are displayed like that), though I'm almost certain that the video card has nothing to do with it as the problem began to occur a long time after I got this computer and threw Tremulous on it. It only occurs in Tremulous, no other games give me this problem.
The actual problem is that I'll be playing Tremulous and I'll want to minimize for one reason or another to get to my desktop or other applications. When I do this, more often than not my desktop will be distorted and most of it will appear fragmented and in small squares. I wish I could post a picture but I can't, as using Print Screen simply takes an image of how the desktop is normally, even through the distortion. Anyhow, my desktop and everything that might be opened on it is basically unreadable. The only way to fix it is to maximize Tremulous again by clicking a little ways to the right of where it, through the distortion, tells me the Tremulous tab on the bottom is. And I repeat this minimize/maximize process until I get lucky and my desktop comes up clearly, and this actually doesn't take all that many attempts actually, but it can be very frustrating. There are occassions where I have to do /vid_restart in Tremulous or the issue will not fix. The alt tab way of minimizing is no different either.
As far as I know, the problem started happening when I began using Tremfusion, and was still there when I switched to the MG Client. I cannot simply place the blame on either of those two clients, because I have no clue if it really is related to them or if it was an error that popped up from something else. Still, thanks in advance for any help I may receive on fixing this irritating problem.
P.S. I might as well also add that a much more minor problem I have is that when I am minimized and looking at my desktop, I will often click a tab on the taskbar, whether it is for Tremulous or another application, and if Tremulous is running my mouse will often just teleport to the upper left corner and I have to keep clicking what I want to see until it actually does it instead of doing that. It's nowhere near as annoying as the main issue I posted on, however, so don't trouble yourself too much in posting on this one.