linux radeon r600g graphical distortion

when playing minecraft with the opensource radeon (r600g) driver on a HD5850, I get this error in the console once in a while:

 Client> radeon: The kernel rejected CS, see dmesg for more information. 

with this output in dmesg:

 [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -12!  

the screen is heavily distorted for a moment, except for a few objects which still display fine.
The other objects render over each other (as if you have a crashed program and move a different window over it and it keeps parts of the content from the other window)

I'm not exactly sure if this is a minecraft related bug, but as I only see this weird behaviour with minecraft and no other graphical application, I'm posting it here.

(The attached screenshot is from a modded minecraft 1.5.2 version with liteloader and weCUI; I wasn't fast enough to capture one when I tested it with vanilla 1.5.2 and 13w21a, but I can assure you that it happens there too)