Vista - slow internet but fast peer to peer

hi guys,

recently IE has become excruciatingly slow to load pages and sometimes will not load at all.

Running Visa Business 32 bit with 2GB ram - all was fine until 2-3 days ago.
2 flatmates (one vista one XP) have no problems at all so this seems specific to my machine.
No real difference if wireless or cable connection to router.
I have 3.5MBps connection (tested), can use limewire at very high download speeds.
I can ping an overseas website in approx 20ms.

Outlook appears to be fine.
MSN Messenger appears to be fine

No excess usage of memory and resources that I can see, and can see no strange processes running (not that I'm an expert)..

Have reset IE settings.
checked all adaptors are up to date with drivers etc..
Windows update all good
Disabled Zonealarm firewall
run full AVG virus and spyware checks
disabled Limewire
Installed Firefox - same issue!
Defraged disk
ran disk cleanup and diagnostics - no identified issues
windows defender found no issues.
windows firewall disabled.

Seriously considering installing XP - but would I need to do a full rebuild for this?

Thanks if you can help,
Dave