I have the EXACT SAME problem.
But before that a little prelude.
Intel P4 3Ghz machine, with 1 GB RAM.
Used to have 865G motherboard, but the board conked and got a "degrade" to Intel 845G chipset (so that I could utilize the Hard disc, processor and ram, and cabinet).
No additional graphics card.
I had PCLOS 10.07 live CD. Ran it via live environment. The live CD ran for two days continuous.
I recovered my data to external disc.
Meantime I thought of updating myself on PCLOS versions.
Saw that PCLOS 11.09 is out. So why not begin with it instead of 10.07
Now the problems started right from the live environment.
Display suddenly freezes.
The mouse pointer can be moved. And I believe the applications can be "minimized" (but you still see them on screen).
Somehow managed to install it on HD.
However, the problem persists.
And it happens every time I use Synaptic, or Appearance settings. (Let me see if there is anything else also triggering).
Just for fun I installed this add-on to firefox: https://addons.mozilla.org/en-US/firefox/addon/macosx-theme-firefox-4-linu/?src=search
AND I got the same freeze EVERY TIME I opened / started FF.
Ultimately had to start FF in safe mode and disable the extension.
The display freezes. The mouse pointer is visible and can be moved though.
Keys don't produce any desired effect.
Ctrl+Alt+Bcksp doesn't work
Ctrl+Alt+F1..F8 doesn't work
REISUB works though
The PC seems to be working though, because once: the display froze in the middle of software update (FF 6 to 9, flash-player update). And after twiddling my thumbs, staring the frozen screen for a while I decided to reboot - and lo! FF had transformed to version 9.
Looks like its a graphics issue. Intel Drivers?
The problem was not there with PCLOS10.07