[ubuntu] No network after 10.04>12.04 upgrade

I seem to have lost my previously working network connection after upgrading to 12.04 from 10.04.

I get the following upon booting:

Waiting for network configuration...

then

Waiting up to 60 more seconds for network configuration...

then

Booting system without full network configuration...

I'm not even sure where to start looking as this used to work perfectly.

Thanks,

Keith