On Fre, 2012-10-26 at 19:15 +0000, Frederik Himpe wrote:

When I restart my display manager (GDM) from tty0, I get a corrupted image where parts of the X display before I restarted GDM become visible on both the newly started X server instance as on tty0. When moving the mouse in X, the current (correct) image around the cursor is replaced by the image which was shown before X was started.

01:00.0 VGA compatible controller [0300]: Advanced Micro Devices [AMD] nee ATI PITCAIRN PRO [Radeon HD 7800 Series] [1002:6819] (prog-if 00 [VGA controller]) Subsystem: PC Partner Limited Device [174b:e218] Flags: bus master, fast devsel, latency 0, IRQ 48 Memory at e0000000 (64-bit, prefetchable) [size=256M] Memory at f7d00000 (64-bit, non-prefetchable) [size=256K] I/O ports at e000 [size=256] Expansion ROM at f7d40000 [disabled] [size=128K] Capabilities: [48] Vendor Specific Information: Len=08 <?> Capabilities: [50] Power Management version 3 Capabilities: [58] Express Legacy Endpoint, MSI 00 Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+ Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?> Capabilities: [150] Advanced Error Reporting Capabilities: [270] #19 Capabilities: [2b0] Address Translation Service (ATS) Capabilities: [2c0] #13 Capabilities: [2d0] #1b Kernel driver in use: radeon

dmesg, .config, lspci and a picture showing a tty0 with parts of the image corrupted by the image of the GDM screen before it was restarted, can be found at http://artipc10.vub.ac.be/~frederik/linux-3.7-rc2/

Please also provide the Xorg.0.log file from after you restarted gdm.