M600 unable to detect network.

[ownsu]

Hi guys, I need some help with SE M600i. I had the phone about 4 month now. It works fine until 2 days ago. All the sudden, it won't pick up any signals. It can't find any network at all. It just say searching..... When i check the connection, it just says GPRS: (unavailable). I also went to menu-> tool->control panel-> connections ->Mobile networks. and when i do search for new network, it wont pick up anything. At first I thought it was my sim card. But i insert it to my old SE k750, it works fine. So i'm not too sure what is going on.

I did not install anything on my M600 or drop my phone when the this happen. anyone has any idea what i should do.

Thanks