No Sim Card Detected after iOS 5.0.1 Update

After updating my iPhone 4G to iOS 5.0.1, I am seeing a no sim card message. I tried to remove my sim card then insert it back. Luckily, it works! But there are times that the message is still appearing. I want to know if there’s anyone here who has the same problem. If so, how did you able to manage it? I need help.
Thank you.
