Had a similar problem last week with my 8900. I installed OS 5 and then, when phone ran out battery, when Icharged back, got a message Invalid SIM card. Installed OS 4.6.1.231 back and the problem remained. Had to replace the SIM card. And now the OS 5 is not available anymore from the Desktop Manager 6.0.0.43. It shows OS 4.6.1.231 as the latest.
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