Thanks frenzy

Two computers can access the internet. The problematic one cannot do so but can access the home network.

I don't think it's the firewall since it allowed stuff through for at least an hour on Limewire before it suddenly lost connection, and the other 2 computers have the same firewall and AVG settings and they allow both access to the internet and to Limewire as I write.
I have restarted the problem computer at least once before and after posting.

2) All 'Local Area Connection' properties are the same on all three computers.

3) All firewall settings permit Limewire as an 'Exception'.

I await your next words of wisdom.

Thanks,
Joe