Starting unity causes a repeatedly flashing white screen to appear on ATI MobilityRadeon

Binary package hint: xserver-xorg-video-ati

I have an ATI MobilityRadeon X1600 on my Toshiba laptop. Running maverick with all updates. When I boot into the Unity UNE session from GDM, I get a white screen that keeps flashing every second or so. CAnnot do anything, the only option is to switch to a VT and restart GDM to log into the normal GNOME session.

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: xserver-xorg-video-ati 1:6.13.1-1ubuntu5
ProcVersionSignature: Ubuntu 2.6.35-21.31-generic 2.6.35.4
Uname: Linux 2.6.35-21-generic i686
Architecture: i386
CheckboxSubmission: 5e476a0872a6160d4830741693075266
CheckboxSystem: 1e11ce1f0b739629ea3e4cbfa4fff3ab
DRM.card0.LVDS.1:
 status: connected
 enabled: enabled
 dpms: On
 modes: 1280x800 1280x720 1152x768 1024x768 800x600 848x480 720x480 640x480
 edid-base64: AP///////wBMozM2AAAAAAAPAQOAIRV4Cof1lFdPjCcnUFQAAAABAQEBAQEBAQEBAQEBAQEB7hoAgFAgEDAQMBMAS88QAAAZAAAADwAAAAAAAAAAACOHAmQCAAAA/gBTQU1TVU5HCiAgICAgAAAA/gBMVE4xNTRYMy1MMDYKAHA=
DRM.card0.VGA.1:
 status: disconnected
 enabled: disabled
 dpms: On
 modes:
 edid-base64:
Date: Fri Sep 17 21:11:59 2010
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
MachineType: TOSHIBA TECRA A7
PccardctlIdent:
 Socket 0:
   no product info available
PccardctlStatus:
 Socket 0:
   no card
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.35-21-generic root=UUID=ba586c06-64e7-4734-a35f-5320ea8063a4 ro quiet splash
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.utf8
 SHELL=/bin/bash
SourcePackage: xserver-xorg-video-ati
dmi.bios.date: 08/30/2006
dmi.bios.vendor: Phoenix Technologies LTD
dmi.bios.version: 2.00
dmi.board.name: MPAD-MSAE Customer Reference Boards
dmi.board.vendor: Intel Corporation
dmi.board.version: Not Applicable
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 1
dmi.chassis.vendor: No Enclosure
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnPhoenixTechnologiesLTD:bvr2.00:bd08/30/2006:svnTOSHIBA:pnTECRAA7:pvrPTA71E-09401CAR:rvnIntelCorporation:rnMPAD-MSAECustomerReferenceBoards:rvrNotApplicable:cvnNoEnclosure:ct1:cvrN/A:
dmi.product.name: TECRA A7
dmi.product.version: PTA71E-09401CAR
dmi.sys.vendor: TOSHIBA
glxinfo: Error: [Errno 2] No such file or directory
system:
 distro: Ubuntu
 codename: maverick
 architecture: i686
 kernel: 2.6.35-21-generic