Problem solved, but
 

not quite sure why!

D-Link wireless router, Tiscali ADSL, UK.

Connection not working, user had contacted ISP who said all was fine and PC World (I know) who told him his browser was corrupted and they would have to reinstall Windows :rolleyes:

Browser was fine, a browse through HJT and trying Firefox confirmed this.

Connection to router was fine but no connection to the net itself was coccurring. On checking the router's settings, I noticed upnp wasn't selected, so I selected it to see if it changed anything, and hey presto, net access was resumed.

I would really appreciate any suggestions as to why this worked, what purpose upnp has in a router, and why/how this setting could have been changed by a user who didn't even know how to access the router's config pages!

Thanks in advance, Ben

UPNP is universal plug and play which automatically detects
plug and play hardware.
It is nesessary for some routers and not others.
It probably got turned off by a security update from
windows update.