Computer hangs unexpectedly and permanently

[korso19]

Binary package hint: xorg

Hi,
I'm using ubuntu Jaunty Jackalope on my Acer 5620 with the following configuration.

Intel core 2 duo processor T5450 (1.66 GHz, 667 MHz FSB, 2 MB L2 cache)
15.4" WXGA LCD
Mobile Intel Graphics Media Accelerator X 3100
2 GB DDR2
250 GB HDD
DVD-Super Multi DL
802.11a/B/g WLAN

As the summary of this bug says, the computer freezes unexpectedly and there is nothing that I can do other than press the power button and put off the PC. Sometimes it happens when I open firefox, sometimes when I open VLC to watch a movie and sometimes it happens with just any window that I open and very unexpectedly.
The only option left is to shut down the system using the power button. Can anybody help me out with this?

ProblemType: Bug
Architecture: i386
DistroRelease: Ubuntu 9.04
Package: xorg 1:7.4~5ubuntu18
ProcEnviron:
 LANG=en_IN
 SHELL=/bin/bash
ProcVersion: Linux version 2.6.28-13-generic (buildd@palmer) (gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4) ) #44-Ubuntu SMP Tue Jun 2 07:57:31 UTC 2009
SourcePackage: xorg
Uname: Linux 2.6.28-13-generic i686