I had it happen to mine way too often. So much so that I had to send my iPhone 4 back to Apple for a replacement! Trust me, if yours gave you the error once, it will most likely give it to you again! The problem is the holder is made in such a way where it doesn't provide sufficient stability to where the SIM card is kept undisturbed against the metal contacts within the iPhone. Prior to this message, I reseated my SIM card due to posts on the internet recommending that this would resolve some reception issues. After I did that, the "No SIM card installed" error would appear randomly at first but more frequently before I decided to exchange it. On a really good note, I use to have pictures that came out yellowish when I turned on flash in a fairly darkened room but now with this replacement, it's perfect.
Originally Posted by bbaggins
I did find a way to successfully remedy this situation with a jerryrig fix for those who don't want to chance getting a replacement iPhone 4 with other problems. What you have to do is turn the SIM card holder upside down and locate the notch on the inside part that falls in line with the cut out area at the bottom of the SIM card spot on the phone (when the SIM card holder is removed, you can see what I'm talking about perfectly). Place a few thin strips of double-sided tape on the notch area of the SIM card holder as this will stabilize the holder so it won't occillate or move within the phone causing the metal contacts to lose their connection. Before I sent my replacement in, the SIM card error was happening 5 minutes after I put the SIM card back in the phone. After I tried this fix, it never happened again for about 2 days until I received my new iPhone 4. The reason I didn't keep it is I don't feel I should have to "jerryrig" a fine product such as this just to get it to work. I'm sure many of you will feel the same way.