I've changed to a different phone company, but my Zero won't work with the new company. I type the PIN-code, and it accepts that, but then it just says "incompatible handset", and won't let me use the mobile net.
The Zero did work with the old company. Also, I've put the SIM from the new company into an old Sony Ericsson phone, and it works fine in that phone.
It seems to me that the new SIM is somehow incompatible with the Zero. The new phone company does have one unusual policy: they don't accept customers with 2G phones, only 3G phones allowed. Could it be that this policy is coded into the SIM, and that this code confuses the Zero?