I just installed Widelands game (build15) on the new computer with following hardware:
 * ASUS P8H67 revision 3.0 motherboard - BIOS 1003
 * Intel Core i5 2500K CPU
 * Gigavyte GV-R575SL-1GI GPU (AMD Radeon HD 5750)
 * 8 GiB DDR3 memory

I get this bug when I start the game. When the game comes up for the first time the image is distorted. To get image back to normal I have to switch to some other console, with Ctrl+Alt+F1 for example, and than back to the console with X11. Then the image is OK and I can play the game. When I start the game for the second time the image of the last visited non-x console is displayed. But this is juts image, it appears it doesn't actually switch to that console, just displays image of it and I still have to use keyboard to switch to non-X console and back to console with X to fix the image.

I've also discovered a workaround for this behaviour. If I start the game from terminal emulator (KDE Konzole) with "SDL_VIDEODRIVER=x11 widelands" there is no problem. In this case the game first tries to use X11 and without the option it tries to autodetect what to use so it looks like the bug happens when probing other modes.

The software used is:
 * Linux kernel 3.0-rc4
 * Widelands build15
 * mesa git-42e7a13
 * libdrm from git
 * xf86-video-ati from git
 * xorg-server 1.10.99.901
 * libsdl 1.2.14
 * sdl-gfx 2.0.22