The odd thing is that when it freezes and gets stuck, I can open Outlook Express and check my emails fine, no problem with the connection, just the browsers stopping and freezing.
OK, so it's a HTML protocol specific issue, not something more generally wrong with DNS, routing or the IP stack.
Assuming that you're running a home PC connected direct to an ISP it's not a problem with you office proxy. If it's a problem with your ISP's proxy you're unlikely to be the only one affected, and one might have expected them to fix it in a day or three. Maybe check that your proxy settings are correct anyway (in most cases "off" will be correct).
Something mangled in the browser cache? Delete everything you can find. But this is unlikely to be the cause if it affects more than one browser.
Which leaves a more local proxy or other protocol specific issue. Such as
- A proxy running on your machine
- A virus checker running on your machine
- A virus or other malware running on your machine
- A firewall running on your machine
I'd feel inclined to find and clobber as many of those as possible. But first, if it were me doing it, I'd run a network sniffer to see what is actually going in out out of your box, both generally when browsing and specifically at the point of failure, as this might give some clues as to which of the above is the problem.