Eseries / Communicators :: E72 Sim Card Registration Failed

I woke up this morning, my phone was fine, I surfed the itnernet, checked my messages etc. I then got the bus to work, during the journey the connection dropped (this sometimes happens but it always comes back after 30 secs or so) after a while the phone said "sim card registration failed".I restarted the phone, no luck.I took the phone apart, removed the sim, put everything back, no luck.I put the sim in another phone, that worked.I put a different sim in my own phone, no luck.I reset the phone to factory settings then put in the sim, no luck.I restored the phone, no luck.