Mouse pointer surrounded by strange colored box, then Vista freezes

Ok so this is really strange. I've been using Vista for 3 months with no problems on my Dell Latitude D620. Yesterday I went away from the computer for a while then returned and I noticed Vista unexpectedly restarted. I went through the event logs and couldnt find any errors. I figured it was a fluke... Started using the machine again and for no reason again, a strange colored box appeared to the right hand bottom corner of the mouse. At that point the machine froze. Couldnt do anything at all. What's also wierd is after I restarted, the entire Dell screen got all funky with strange colors... Windows would not start in Normal bootup mode. When I tried, the system flickerd white, then blue screened. I hadnt installed any new hardware so I wasnt sure what the issue could be. I restarted the machine again, this time booted with last known good config. The system worked for a few hours then the same thing happened.

Finally I decided to try system restore. I noticed a Windows security update yesterday and restored to the point in time before that update. The system seems to be functioning ok now but I am concerned that this is something more serious. Has anyone else had a similar problem?