I've been having garbled screen problems on a Gateway LT3103u on Ubuntu for a while. I just did a fresh install of Ubuntu 11.10 and continue to have issues. I installed xubuntu-desktop in case the issues had to do with the sophisticated GNOME graphics. The problem is less bad, but it's still there. After a few minutes of using XFCE, the screen gets garbled. I assume this has something to do with the graphics card, but I don't know how to go about troubleshooting something like this. Where should I start?

Update: Here is the description of the VGA card from lspci -vvv:

01:05.0 VGA compatible controller: ATI Technologies Inc RS690M [Radeon X1200 Series] (prog-if 00 [VGA controller]) Subsystem: Acer Incorporated [ALI] Device 028c Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- SERR- [disabled] Capabilities: [50] Power Management version 2 Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-) Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME- Capabilities: [80] MSI: Enable- Count=1/1 Maskable- 64bit+ Address: 0000000000000000 Data: 0000 Kernel driver in use: radeon Kernel modules: radeon

Update: Setting GRUB_CMDLINE_LINUX="nomodeset" in /etc/default/grub seems to have fixed it in both Ubuntu and xubuntu-desktop. I will test it for a day or so to see if the problems recur and then post more detail with some links to an explanation.

Update 2: It is possible to use this fix for Nvidia card (GTX 260) when graphics is defective after 11.10 upgrade/install? First few restarts was graphic ok, then after few restarts begins suddenly be defective and it stay so. I must returned to 11.04 because this problem and I wait for 12.04. So I hope in this fix.