Browsers just fade and die....

Ok, I am at my wits end so I've been recommended to try this forum for a solution.

When using the internet, after any given period of time, could be 30 seconds, could be 30 minutes, my connection just hangs and fails to do anything. The only way I've found to correct the problem is to reboot the PC.

I don't think the problem is with my ISP (for the record I'm on fixed wireless) - they've checked and checked and concluded that the problem is with my PC.

I'm using Opera but the problem is browser independent and when it occurs nothing else needing the net works either (Messenger, Skype etc.). The manifestation in Opera is that when I click a link the progress bar just sticks on either '0Kb' or '0/0 Elements'. Whenever it happens, the status icon at the bottom of the screen indicates that my internet connection to my ISP is fine.

Nobody seems to know so if anybody on here has any ideas I'd be very grateful. Oh and if you do have any ideas, please spell them out in idiot speak. I'm only average when it comes to the tech stuff!

Thanks.