Sounds like a bad installation, try the following:
1. Restart the terminal (if you have not already) in the sim slot is a dot that says off, you press it with a fine needle.
2. If this does not work, try entering the recovery and do a wipe cache
3. If this does not work, you could take it for service or do a hard reset (losing your data)
First try:
You could also try PC Companion (official Sony software, find it from their website, in the section of service), to help restore mobile.