Iphone 3GS unable to detect s card

Hi everyone, out of a sudden my iphone 3GS was unable to detect me SIM Card anymore. When I reset the phone, it shows searching.. on the upper left hand corner. But if i take out the sim card tray and put it back in again, it will remain as No Sim until i reset my phone again. I tried to restore my phone hoping that it would solve the issue but instead, i ran into another problem. I am unable to activate my phone through itunes due to my phone not detecting my SIM Card. Anyone able to give me advise on this ?
Additional Info,
I am residing in singapore and using starhub.
My phone is on version 4.1
Acer Aspire 6920G Windows 7