There is a bug in handling the thread instruction inside lv321av.sys driver which is not properly handled. It tries to derefence a null pointer (memory location is no longer valid). Probably, due to bad thread programming, the race condition has occurred. Worst, the bug has not be solved by the device manufacturer of Logitech Orbicam used as OEM webcam in Acer laptop models. Try to see any update for this device driver.

Windows XP SP2 was released on 25 August 25 2004.
Windows XP SP3 was released on 24 March 2008.
Windows Vista SP1 was released on 4 February 2008.

Reported cases after Windows Vista SP1:

http://forum.notebookreview.com/showthread.php?t=258426

There are a few reported cases of driver problem after the that release (possibly after the SP3 update):

http://www.fixya.com/support/t539019-oribc...ng_system_crash

In a French forum, it says the person is suffering BSOD (écran bleu = bloqué sur l'écran bleu = stucked on blue screen of death) with the driver.
http://forum.telecharger.01net.com/telecha...messages-1.html

There are a few cases occurred after update from Windows XP SP1 to Windows XP2

http://forum.notebookreview.com/showthread.php?p=1284052

http://forum.notebookreview.com/archive/in...p/t-207910.html

So, this driver problem started regardless of every service pack update.
Try to get the latest Vista driver for your Orbicam from here:

http://www.windows-vista-update.com/Logite...dows-Vista.html

The given link redirects to a paid/subscribed RadarSync service.

Another link redirects to a paid/subscribed DriverZone.com

http://www.theacerguy.com/2007/04/14/orbic...-windows-vista/

So, best way is to get the latest orbicam driver for your laptop model from Acer website.

Another possible hint to the problem: