it crashes when i try to go into "expo mode"

dmesg:
radeon 0000:01:00.0: r600_cs_track_validate_cb offset[0] 32841 too big
radeon 0000:01:00.0: r600_packet3_check:1247 invalid cmd stream 1373
[drm:radeon_cs_ioctl] *ERROR* Invalid command stream !


taken from xorg.log:
Backtrace:
[ 15872.220] 0: /usr/bin/X (xorg_backtrace+0x28) [0x4a0148]
[ 15872.220] 1: /usr/bin/X (0x400000+0x631a9) [0x4631a9]
[ 15872.220] 2: /lib/libpthread.so.0 (0x7f56a8fd8000+0xf150) [0x7f56a8fe7150]
[ 15872.221] 3: /usr/lib/libpixman-1.so.0 (0x7f56a806b000+0x4aa61) [0x7f56a80b5a61]
[ 15872.221] 4: /usr/lib/libpixman-1.so.0 (0x7f56a806b000+0x53560) [0x7f56a80be560]
[ 15872.221] 5: /usr/lib/libpixman-1.so.0 (pixman_blt+0x78) [0x7f56a809da58]
[ 15872.221] 6: /usr/lib64/xorg/modules/libfb.so (fbCopyNtoN+0x2ae) [0x7f56a5ea3cce]
[ 15872.221] 7: /usr/bin/X (miCopyRegion+0x1d5) [0x543e95]
[ 15872.221] 8: /usr/bin/X (miDoCopy+0x44e) [0x54446e]
[ 15872.221] 9: /usr/lib64/xorg/modules/libfb.so (fbCopyArea+0x46) [0x7f56a5ea31e6]
[ 15872.221] 10: /usr/lib64/xorg/modules/libexa.so (0x7f56a5c7b000+0x10ed3) [0x7f56a5c8bed3]
[ 15872.221] 11: /usr/bin/X (miCopyRegion+0x1d5) [0x543e95]
[ 15872.222] 12: /usr/bin/X (miDoCopy+0x44e) [0x54446e]
[ 15872.222] 13: /usr/lib64/xorg/modules/libexa.so (0x7f56a5c7b000+0x8666) [0x7f56a5c83666]
[ 15872.222] 14: /usr/bin/X (0x400000+0xd4dc4) [0x4d4dc4]
[ 15872.222] 15: /usr/bin/X (0x400000+0xb345d) [0x4b345d]
[ 15872.222] 16: /usr/bin/X (0x400000+0xb4555) [0x4b4555]
[ 15872.222] 17: /usr/bin/X (0x400000+0x2f22c) [0x42f22c]
[ 15872.222] 18: /usr/bin/X (0x400000+0x24cab) [0x424cab]
[ 15872.223] 19: /lib/libc.so.6 (__libc_start_main+0xfd) [0x7f56a76a0bbd]
[ 15872.223] 20: /usr/bin/X (0x400000+0x24829) [0x424829]
[ 15872.223] Bus error at address 0x7f56a1c4502c
[ 15872.223]
Fatal server error:
[ 15872.223] Caught signal 7 (Bus error). Server aborting