A number of iPhone users have been writing in on the Apple support forums that they are having trouble connecting to Bluetooth devices after upgrading to the new iOS 5 operating system. What happens typically is that the iPhone may not be displaying the Bluetooth icon on the top of the screen even though you have the Bluetooth option turned on in the Settings option. Also, the iPhone may refuse to recognize any other Bluetooth enabled devices in the vicinity which means you may not be able to connect to any other device.
There is a simple fix for this though. What you need to do is go to Settings -> General -> Bluetooth and turn the option Off and then turn On again one more time. Your iPhone will start recognizing Bluetooth enabled devices once again. So how frequently will you see this problem? Every time you restart your iPhone. In any case, this is a major irritant for those of you who frequently connect your iPhones to Bluetooth devices. And if you own a new iPhone 4S that has battery issues as well, good luck since you will also have to deal with the phone conking out every now and then.
Let’s hope Apple fixes this issue soon in the next update.