[etccarmageddon]

found a possible answer here...

http://www.3gnewsroom.com/phorum-3.4...=16570&t=16570

the CPW "3" nokia 7600 is set to lock onto a 3G network, in preference to a GSM network, if available. So with 3, it will lock onto the 3 3G network in preference to the O2 network; with Orange, it will try to lock onto the Orange 3G network in preference to the GSM network, etc, etc.....

If there is no 3G coverage for that network, then it has no problems connecting to the GSM network.

If there is 3G coverage, say for Orange 3G, the handset tries to connect to it, and as the SIM is not identified as a Orange 3G tester SIM, it will be booted off the network. The handset doesn't know what to do about that because its still reading a strong 3G signal, instead of dropping down to the GSM network, it will try reconnecting to the 3G network.

Simfree Nokia 7600s sourced elsewhere don't have this problem as they haven't been engineered for 3.

At least thats my interpretation of whats happening.