Description of problem:
Starting compiz hangs my laptop. It responds to ICMP pings, but I am unable to ssh in. The laptop is a Toshiba Satellite Pro A210, its graphics chip is:

01:05.0 VGA compatible controller: ATI Technologies Inc RS690M [Radeon X1200 Series] (prog-if 00 [VGA controller])

Using netconsole I got this BUG message:

[drm:radeon_object_list_reserve] *ERROR* radeon: failed to reserve object.
[drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation !
------------[ cut here ]------------
kernel BUG at drivers/gpu/drm/ttm/ttm_bo.c:133!
invalid opcode: 0000 [#1] SMP 
last sysfs file: /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
CPU 1 
Modules linked in: netconsole configfs fuse nfsd lockd nfs_acl auth_rpcgss exportfs sunrpc ip6t_REJECT nf_conntrack_ipv6 ip6table_filter ip6_tables ipv6 cpufreq_ondemand powernow_k8 freq_table dm_multipath uinput ata_generic snd_hda_codec_realtek pata_acpi snd_hda_intel sdhci_pci arc4 ecb sdhci snd_hda_codec ath5k amd64_edac_mod snd_hwdep snd_pcm mac80211 firewire_ohci snd_timer video ath r8169 firewire_core snd mmc_core output k8temp edac_core crc_itu_t soundcore pata_atiixp i2c_piix4 hwmon mii cfg80211 shpchp snd_page_alloc rfkill joydev xts gf128mul cryptd aes_x86_64 aes_generic dm_crypt radeon ttm drm i2c_algo_bit i2c_core [last unloaded: scsi_wait_scan]
Pid: 1558, comm: Xorg Not tainted 2.6.31-0.199.rc8.git2.fc12.x86_64 #1 Satellite Pro A210
RIP: 0010:[<ffffffffa0047fe3>]  [<ffffffffa0047fe3>] ttm_bo_unreserve+0x47/0x109 [ttm]
RSP: 0018:ffff880063d47b88  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff880037ac3ea8 RCX: ffffffffa0047fd2
RDX: ffff880037aca418 RSI: ffffffffa0047fd2 RDI: 0000000000000246
RBP: ffff880063d47bb8 R08: ffff880063cbd1e8 R09: 0000000000000000
R10: ffffffff81e182c0 R11: 0000000000000000 R12: ffff880073ce37a8
R13: ffff880063d47c18 R14: ffff880037aca048 R15: ffff8800652e6b68
FS:  00007f982970a7c0(0000) GS:ffff88000286c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001915a08 CR3: 0000000037c33000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process Xorg (pid: 1558, threadinfo ffff880063d46000, task ffff880063cbc940)
Stack:
 ffff880063d47c28 00000000a9b58d22 000000000000004b ffff880053080688
<0> ffff880063d47cd8 ffff880063d47c18 ffff880063d47bd8 ffffffffa0077e65
<0> ffff8800652e6bf8 00000000a9b58d22 ffff880063d47c08 ffffffffa0077eb4
Call Trace:
 [<ffffffffa0077e65>] radeon_object_unreserve+0x21/0x37 [radeon]
 [<ffffffffa0077eb4>] radeon_object_list_unreserve+0x39/0x62 [radeon]
 [<ffffffffa0077f8c>] radeon_object_list_unvalidate+0x78/0x97 [radeon]
 [<ffffffffa00851ad>] radeon_cs_parser_fini+0x31/0xfb [radeon]
 [<ffffffffa00858df>] radeon_cs_ioctl+0x179/0x1a6 [radeon]
 [<ffffffffa0085766>] ? radeon_cs_ioctl+0x0/0x1a6 [radeon]
 [<ffffffffa0015b18>] drm_ioctl+0x23d/0x2fd [drm]
 [<ffffffff811435a0>] ? do_sync_read+0xfa/0x14b
 [<ffffffff81152aac>] vfs_ioctl+0x7e/0xaa
 [<ffffffff81153021>] do_vfs_ioctl+0x4aa/0x506
 [<ffffffff811530e2>] sys_ioctl+0x65/0x9c
 [<ffffffff81012f42>] system_call_fastpath+0x16/0x1b
Code: 89 45 d8 31 c0 48 8b 1f 49 89 fc 48 81 c3 00 01 00 00 48 89 df e8 58 ef 4b e1 41 8b 84 24 58 01 00 00 49 8b 54 24 08 85 c0 75 04 <0f> 0b eb fe 41 f6 84 24 02 01 00 00 20 75 6d 49 8b bc 24 20 01 
RIP  [<ffffffffa0047fe3>] ttm_bo_unreserve+0x47/0x109 [ttm]
 RSP <ffff880063d47b88>
---[ end trace c807ae7874996552 ]---

Version-Release number of selected component (if applicable):
kernel-2.6.31-0.199.rc8.git2.fc12.x86_64
xorg-x11-drv-ati-6.13.0-0.2.20090821gitb1b77a4d6.fc12.x86_64
xorg-x11-server-Xorg-1.6.99-45.20090903.fc12.x86_64

How reproducible:
always

Steps to Reproduce:
1. Use desktop-effects to enable compiz
2. Wait about 2 seconds
  
Actual results:
Compiz starts, its decorations appear, but in a moment the machine locks hard.

Expected results:
No hangs.