Just noticed a problem with my iPad after coming back from an overseas trip. I was using a Telecom SIM card in the US, with data roaming turned off, and connected to AT&T. I wasn't able to connect to Telecom 3G data after arriving back in NZ. After some poking around, I noticed that the APN was mysteriously missing from the cellular data settings (internet.telecom.co.nz). Re-entry of this setting followed by a re-start fixed the problem.
Anyone else come across this, and more importantly, know how to make the APN setting stick?
I'm using 4.2.1 and upgraded a few days before my recent trip to the US. The same problem occurred after a trip to Hong Kong last month when I was still using iOS 3.2 on my iPad. So it doesn't appear to be a problem with the upgrade, as I didn't have any problem in NZ immediately after the upgrade.
By comparison, my iPhone on vodafone didn't show any problems after returning to NZ this morning.