I went to the Wisconsin Dells for a long weekend with my wife and a couple we know. We had a good time. I brought my iPhone and showed it off (as best I could). The main problem is that the place we were staying had poor coverage. Barely one bar or the infamous "No Service" message would display in the upper left hand corner of the display.
I did notice someone else chatting away on their cell phone in the cabin across from us with no problems. My best guess: they have a different cellular provider. My wife's plain-jane cell phone had trouble too (but she uses AT&T too).
This is where things get a little strange: We went into town and I expected my coverage to return. It did not. Though my wife's did! That set my mind in motion. What if I cold-booted my iPhone? Turn it completely off, wait abit, and then turn it back on. That did the trick. I now had good signal strength. When I went back to the cabin area out of town though the signal strength went away again.
My conclusion: When using an iPhone in a low or no coverage area, the phone can get confused when entering a good coverage area and behave as if it's still in a low coverage area. This could be a hardware or software issue. I hope it is a software issue because then it can be corrected on our existing phones. At least I can get things jiggered back so they will work by turning the phone completely off and then restarting it! Have you run into anything like this?