new avg 8 installed ---> computer freezes

Hi,
I'm a newbie here, I hope you can help me...

My computer freezes as soon as the first command. Right or left click don't work, If the pointer is on an icon, it stands as "busy".

The only thing i can do is switch it off and starting it again, which worked for a day but now it won't not freeze! Computer is useless!
The only change I can think of is that I installed the new avg 8. I did it because my computer said that my anti-virus was not up to date and it wouldn't update itself! I also have spybot anti-virus.
I checked for virus soon after installing that new avg 8, in case i got one when i was not up to date but the virus scan was clean.

So my questions are, is it possible AVG 8 and that freezing are related, if so, how do I do to fix it? Is it common problem?

I'm using Windows XP on Dell Inspiron 6400

Thank you for your help