iPad WiFi + 3G - iTunes 10 Error

I have had an iPad wifi pretty much since the release. However today I decided to upgrade to the 3G model.
I already had the micro sim for iPad from O2 - so I inserted it and booted up the iPad.
After the initial sync/setup, it said "No Sim" on the screen - even though one was inserted. I tried turning on/off the iPad, resetting, and took the sim out etc, but nothing...

Apparently though, you are meant to update the sim carrier file on the iPad by plugging into iTunes and clicking the "Check for Updates" button. But it gives this error (and yes, it does say iPhone):
"Error 1631: iTunes was unable to search for updates for the network operator settings for your iPhone"

?? Is anyone else getting this issue. I cannot use my data on the iPad as a result... Maybe I should downgrade to itunes 9?

The microsim was from O2 and was a dedicated iPad microsim.
However it turns out that my iPhone microsim DID work in the iPad (signal bars came up) but obviously no Internet access. But when I put the iPad sim into my iPhone, it said "No sim", leading me to the conclusion that the sim is probably faulty. I have ordered another one.

As for iTunes, I downgraded to 9, and was able to update the carrier settings (a popup came up with it, a bit like iPhone one) and it managed to update it. But no 3G until the new sim arrives anyway...

Thanks. Though I can't check the APN settings until I get a working SIM!
I think it only has carrier updates in countries where there is more than one provider(?). I know AT&T are the sole provider, but in the UK we have 4 or 5 choices of carrier. The settings file is probably downloaded based on what Sim you put in.