This I think is a promblem with all nokia 6630s on orange with line 2 with the 345110 02-12-04 software - if you have a line 2 connection on orange it works fine but if you put a pin code on your phone line 2 will vanish and by pressing the hash key you will not be able to select line 2, If you take the pin code off it all works again crazy. If anyone has line 2 on orange on their phone give it a try.
If you use the auto lock on the phone this does work with line 2.
Also if your phone switches off and on/ restting itsself try taking the pin code off as this cures this problem too well it does with my phone.