So after a long time spent in no connectivity to 2G network the phone worked on it for 2 days without any problems and then began not to connect to the 2G network again. In the Profile String section from the Engineering Screen I can see msgs like Downlink Signalling Failure, RAU Failure and T3168 - No assignment.
I don't think those messages indicate a problem, I see them in my own Profile String section. What does your banner show as the network (GSM, gprs, GPRS, edge, EDGE, ...)? You might want to open the Mobile Network Options screen and check the settings for Network Mode, Data Services, and While Roaming.
