Wired networking suddenly stopped on Laptop

[damian]

I've been away using a friends wireless set up (as I have done many 
times before), but I've returned and plugged my laptop into my wired 
network and I can't get emails or any web pages in firefox. I can ping 
the main machine on the network which is always on, but can't seem to do 
much else. Can someone guide me where to look to sort this out?

It's not a physical problem as the laptop is dual boot and XP can still 
connect fine.

Looking forward to your thoughts.

Damian