K750i reboots itself PLEASE HELP !!!

[lucja]

Tonight I found a new interesting thing about this phone. I put in a SIM from another country I have (T-mobile) and here there is no T-Mobile network and the phone won't reboot anymore. I put an inactive Vodafone SIM in (there are Vodafone carrier here) and the k750i reboots upon finding signal. To me seems that this has to do with the network. The carrier somehow soft resets the phone. Or, the phone doesn't reboot with T-Mobile SIM since there is no T-Mobile network and RF circuitry is OFF while with Vodafone SIM network is present and RF circuitry is ON (and probably faulty) and that resets the phone.
Any ideeas?