System freezes when on mobile broadband internet

Hi all,
I recently got a Compaq Presario CQ41 Notebook PC with Windows 7 Home Premium. I have used a mobile broadband stick for online access for over a year on my old XP (and later Vista) Dell, but since I got my new computer it is not going so well. The computer seems to go fine online on various wireless networks, but when I go home and plug in my mobile broadband stick, I go on the net for a bit and after anywhere between 2 and 30minutes suddenly the whole system freezes and I have to force shutdown. It seems to make no difference whether I am on Opera, Explorer or Mozilla.
Does anyone know what I can do about this? Or what is going on?
Thanks (in advance) for your help.

It was a dodo stick, but nevermind! I combed through the other threads to discover that there is some issue with AVG and mobile broadband. I have uninstalled AVG and its working fine. Not entirely sure what to replace AVG with however. Thanks for your help.

THANKS!