I have windows xp pro. Up until about two weeks ago if I was in Firefox and the computer locked I would hit cntl alt del and the END TASK menu would come up Problem solved. Now Crtl alt del has no effect on computer. Nothing comes up. Even if I am not locked up. Why is this. I downloaded an firefox update around that time. Could that be the problem and how do I reslove.
Thank you
Ed

Windows task manager failing to open is one symptom of virus infection.
Does your antivirus program still operate? If so, run a full computer scan.
Check this knowledge base article for tips.
http://support.microsoft.com/kb/129972/en-us

I doubt the FireFox update caused this. If it had there would be an epidemic of complaints. I installed the update and Windows task manager still works on my computer.

Let us know how you are progressing with the problem.

Firefox? Although it has received much so-called 'critical acclaim' I have found it to be extraordinarily slowwww to load and quite temperamental. It could be the knub of your problem.   :-/