Looks like we are in the same boat I get exactly the same error. I started a different thread here:

http://talk.maemo.org/showthread.php...541#post625541

Maybe these threads should be merged?

A workaround is to connect the b-mobile 3G USB modem to a Cradlepoint mobile router then access the connection via wifi. A bulky solution though - I'd much rather use the SIM in the n900 directly.