I have found a bug regarding the UI for Blender 2.56 for Windows (the one provided in the downloads section).

After certain actions (the most consistent for me being opening the user preferences window) the UI stops redrawing properly. I can still do things, but text usually doesn't draw and the panel backgrounds seem to not be cleared, causing the UI elements to simply be drawn over the old ones.

I can fix it by clicking around on buttons I can see until it works properly, but that "fix" only works 2-3 times before it no longer works. After that the only fix is to relaunch.

Most likely, this is an issue with your video card/driver. If you have updated your video driver and turned off any compositing window managers, you might try playing with the Window Draw Method on the System tab in User Prefs.

stiv wrote:

Most likely, this is an issue with your video card/driver.

Odd considering every other program on my computer is perfectly capable of redrawing properly, and even Blender is capable of it until I close the user prefs window which very consistently triggers this bug. I would think that if it were a driver issue that it would cause problems right from the beginning and would cause issues in other programs as well.

Not odd at all considering Blender using OpenGL for all its drawing. Your other programs, games for example, are likely using DirectX or other native Microsoft drawing libraries. If your video card/driver/settings do not do OpenGL well, you will have display issues.

stiv wrote:

Not odd at all considering Blender using OpenGL for all its drawing. Your other programs, games for example, are likely using DirectX or other native Microsoft drawing libraries. If your video card/driver/settings do not do OpenGL well, you will have display issues.

I 99% sure C4D and WoW use OpenGL, and Ogre3D, Irrlicht and my own OpenGL programs run fine as well. Also, the 3D rendering works fine, it's only after I close the user preferences window (or a couple of other things that I can't exactly remember) that this issue pops up, and given the fact that Blender uses a custom UI system rather than using the OS's UI library (or a known working library that abstracts platform differences) it wouldn't surprise me at all if there was a problem in there.

Edit: Downloaded a newer build (2.56.3 r35518) and it's a bit better. It seems as though it's most stable if I have the window redraw set to "overlapped flip." Triple buffered gives the problem and I haven't tried anything else yet.