From var/log/messages :
Oct 24 11:23:05 laptop0 kernel: [ 2952.597447] 
Oct 24 11:23:05 laptop0 kernel: [ 2952.597456] Pid: 930, comm: Xorg Not tainted 2.6.35-22-generic #35-Ubuntu 3093/Presario V2000 (EL088PA#ABG)      
Oct 24 11:23:05 laptop0 kernel: [ 2952.597460] EIP: 0060:[<f86892f1>] EFLAGS: 00013286 CPU: 0
Oct 24 11:23:05 laptop0 kernel: [ 2952.597479] EIP is at radeon_ttm_bo_destroy+0x31/0xa0 [radeon]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597482] EAX: f0c31000 EBX: f0c31000 ECX: 00000000 EDX: 00000000
Oct 24 11:23:05 laptop0 kernel: [ 2952.597486] ESI: f0c31050 EDI: f6a74404 EBP: f15f5d3c ESP: f15f5d30
Oct 24 11:23:05 laptop0 kernel: [ 2952.597489]  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
Oct 24 11:23:05 laptop0 kernel: [ 2952.597499]  f0c31050 f0c31078 f6a74404 f15f5d50 f8225051 f0c31078 f8224fe0 f6a74414
Oct 24 11:23:05 laptop0 kernel: [ 2952.597507] <0> f15f5d60 c0352edd f0c31050 f6a74404 f15f5d74 f822777c f0c31074 f8227710
Oct 24 11:23:05 laptop0 kernel: [ 2952.597514] <0> 00000001 f15f5d84 c0352edd f6a74404 f0c31050 f15f5d94 f82255f2 fffffff4
Oct 24 11:23:05 laptop0 kernel: [ 2952.597546]  [<f8225051>] ? ttm_bo_release_list+0x71/0xb0 [ttm]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597553]  [<f8224fe0>] ? ttm_bo_release_list+0x0/0xb0 [ttm]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597566]  [<c0352edd>] ? kref_put+0x2d/0x60
Oct 24 11:23:05 laptop0 kernel: [ 2952.597574]  [<f822777c>] ? ttm_bo_release+0x6c/0x90 [ttm]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597581]  [<f8227710>] ? ttm_bo_release+0x0/0x90 [ttm]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597585]  [<c0352edd>] ? kref_put+0x2d/0x60
Oct 24 11:23:05 laptop0 kernel: [ 2952.597593]  [<f82255f2>] ? ttm_bo_unref+0x32/0x50 [ttm]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597601]  [<f82276a2>] ? ttm_bo_init+0x1a2/0x1f0 [ttm]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597621]  [<f8689521>] ? radeon_bo_create+0x111/0x240 [radeon]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597640]  [<f86892c0>] ? radeon_ttm_bo_destroy+0x0/0xa0 [radeon]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597667]  [<f869cd36>] ? radeon_gem_object_create+0x76/0xe0 [radeon]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597689]  [<f869ce07>] ? radeon_gem_create_ioctl+0x67/0xe0 [radeon]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597700]  [<c01c645d>] ? t_start+0x8d/0x90
Oct 24 11:23:05 laptop0 kernel: [ 2952.597736]  [<f841b98d>] ? drm_ioctl+0x1ad/0x430 [drm]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597741]  [<c01c645d>] ? t_start+0x8d/0x90
Oct 24 11:23:05 laptop0 kernel: [ 2952.597762]  [<f869cda0>] ? radeon_gem_create_ioctl+0x0/0xe0 [radeon]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597771]  [<c032e636>] ? apparmor_file_permission+0x16/0x20
Oct 24 11:23:05 laptop0 kernel: [ 2952.597781]  [<c0302a84>] ? security_file_permission+0x14/0x20
Oct 24 11:23:05 laptop0 kernel: [ 2952.597790]  [<c02185d2>] ? rw_verify_area+0x62/0xd0
Oct 24 11:23:05 laptop0 kernel: [ 2952.597795]  [<c01c645d>] ? t_start+0x8d/0x90
Oct 24 11:23:05 laptop0 kernel: [ 2952.597799]  [<c0226622>] ? vfs_ioctl+0x32/0xb0
Oct 24 11:23:05 laptop0 kernel: [ 2952.597814]  [<f841b7e0>] ? drm_ioctl+0x0/0x430 [drm]
Oct 24 11:23:05 laptop0 kernel: [ 2952.597818]  [<c0226eb9>] ? do_vfs_ioctl+0x79/0x2d0
Oct 24 11:23:05 laptop0 kernel: [ 2952.597822]  [<c0227177>] ? sys_ioctl+0x67/0x80
Oct 24 11:23:05 laptop0 kernel: [ 2952.597826]  [<c01c645d>] ? t_start+0x8d/0x90
Oct 24 11:23:05 laptop0 kernel: [ 2952.597833]  [<c05c9114>] ? syscall_call+0x7/0xb
Oct 24 11:23:05 laptop0 kernel: [ 2952.597837]  [<c01c645d>] ? t_start+0x8d/0x90
Oct 24 11:23:05 laptop0 kernel: [ 2952.597841]  [<c01c645d>] ? t_start+0x8d/0x90
Oct 24 11:23:05 laptop0 kernel: [ 2952.597910] ---[ end trace e71d0817139ae2dd ]---

Hopefully this helps.