I've been having trouble getting access to anything vaguely "Internety" today when on 2G or 3G instead of WiFi - but I've finally figured out what the problem is.
/etc/resolv.conf pointed DNS queries to 127.0.0.1 and it simply wasn't resolving (the Pre seems to run a caching named). Based on some poking around in the filesystem (under /var) there is another resolv.conf which seems to contain the nameservers allocated by DHCP,but this hadn't made it into /etc.
Editing /etc/resolv.conf to include some real DNS servers (in may case for T-Mobile/Virgin Mobile UK) has solved the issue and 'net access is working again.
Has anyone else encountered a similar problem ?