This bug is actually pretty hard to describe, and even harder to trigger, but it certainly comes up with some frequency.

I think it has to do with the openbox + tint2 + xcompmgr combination I am running, but I can't be sure. It certainly never never happens in KDE. It looks something like this:

It gets triggered when I start an application. I feel like it's okular quite often, but sometimes it's konsole or dolphin or something else. So call it application foo. So I start that application, and its window mostly fails to draw over some part of the screen, like a rectangle, usually in upper left. In fact, nothing gets redrawn in that rectangle anymore while the application foo is running. The lower and right margins of the screen get drawn OK: there I can see the application foo as well as everything else. When I kill the application foo, everything goes back to normal. Sometimes, killing all windows fixes the bug. Other times, restarting tint2 fixes the bug. Sometimes (quite rarely), only killing X fixes the bug, and that is the only thing that always works. Anyone seen anything like that?

Sounds similar to what I occasionally experience with my Debian system. I also have Openbox, tint2 and xcompmgr, but I am not convinced any of those are the problem. For me, the trigger seems to be connected with the file manage and the game Simultrans. If Thunar or PCManFM is running when Simultrans is started a second time it occasionally generates a problem. It never happens the first time the game is started.

Edit
I forgot to mention two things.
It happens with Thunar and PCManFM, but not with Krusader.
The work around I have found to restore a normal desktop is to open an Ace of Penguins game. I have no idea why, but it works.

Ah, finally found it (or something very similar): http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=683556

Looks like it's fixed in 3.5.2. Any news on SlackBuild?

Why not switch to compton, sounds like a compositor problem? Used compton with OB and tint2 for a while with no sweat. You can build it from git with src2pkg and have a package for it very easily, no extra make or configure options. Just src2pkg /path/to/compton/

Wow never heard of compton before. But running it now. OMG, I don't even care if this bug persists. This is just dreamy.

Cool! I started with xcompmgr and thought it was kinda limited especially with transparency options. Here's my compton start up line if you want, but I'm not using transparency but you could tweak it, the main thing that the backend glx solved for me was being able to stop screen tearing on my desktop (Nvidia) and laptop (hd4000) plus it stopped a lot of glitches I was getting while watching video in vlc while using nvidia hardware decoding!

this is the line I use on my desktop(Nvidia):

compton -c -C -r 6 -l -8 -t -8 -m 0.9 -G --backend glx --paint-on-overlay --glx-no-stencil --vsync opengl-swc -b

Indeed, compton is nice, I use it with i3 for some nice transparency effects and smoother workspace switching.
This is my compton command:There is no need for a complicated command line, compton has nice configuration file.

Composite problem or not it definitely good thing to change xcompmgr to compton.
A whole bunch of pluses. Tearing free video, a lot less cpu utilization in OpenGL eg. games and a lot more.