Simple problem, is there a simple answer?

[tsaint]

When I startup win xp, clicking (left or right) items in the taskbar or system tray has no effect. Pressing C-A-Delete will then allow normal clicking on the taskbar and system tray.
 This behaviour may recur later, with a similar fix.
 Apart from latest firefox update, no software installed immediately before the behaviour appeared, about 4 days ago, when I was holidaying in Vietnam (could that be a relevant factor??????)
 My first thought, rationally or otherwise was virus/malware/??? - my school, who own this computer and insist on McAfee have, in their wisdom, somehow disallowed scan on demand, so I can't easily scan for a problem.
 Maybe it's something else, but I can't see any "unusual" processes running from the task manager (to my untrained eye that is)
Thanks for any help
tony

[gexecuter]

If you can somehow disable your antivirus you might wanna give Combofix a try, it has help me a lot in the past in deleting common malware.

[superboyac]

The only time I've encountered something similar to this was when I had a virus/malware.  I wrote about it recently here (last couple of months?).  Something disabled every executable on the pc.  It was horrible.  You couldn't run anything.  Your thing sounds different, so it may be that something is broken and not a virus.  You never know.  In my case, I was forced to reinstall the OS.  Pain in the butt.

I just can't tell from your description if it's a virus or not.  It can go either way.  Sorry for not having helpful info!

[Target]

apologies if I'm teaching you to suck eggs here, but if you have web access (DOH! you CLEARLY do) then online scans can do the AV bit (otherwise there are standalones - Dr Web Cureit, CLAM AV, etc - that can be run from a USB drive

if you can rule out an infection of some sort it's a start

probably also be worth checking your autoruns for any 'strays'...

[lanux128]

something like Process Explorer could give a better picture of what's running from which folder. you can also post the screenshot of that process explorer window here for someone to take a look at. plus as Target mentioned, use a startup manager tool (e.g Startup Control Panel) to identify if there is any new uninvited guest hitching a ride.

[tsaint]

thanks for those suggestions...I'm sitting on the steps outside a library which is closed for xmas to get access, with my eeepc. Boxing day, I'll be back, INSIDE, to try out some of those options. At the moment, I've removed from starting up everything I think is non-essential. Process explorer, on-line scan sound like the options to try next when I can.
Again, thanks, and have a joyful and peaceful Christmas.