I've heard nothing but grumbling when it comes to trying to connect any version of Mac OSX to broadband via USB. Don't be surprised if your set-up is flakey even if you do get all the correct drivers. If I were you, I'd get that lovely iBook off for a repair as quickly as possible.

but can I ask, was there a noticeable change in the iBook's performance when you upgraded it from 10.2 to 10.3?