iPhone Home Button Bug
Several people have been reporting that their iPhone Home button wont always respond when single or double-clicking. It’s possible that it’s software related since most of those reports began after the person installed iOS 4.1.
It was hoped that after you updated to iOS 4.2.1 that the bug would be fixed, but apparently that’s not the case. A possible hardware short or something such as lint getting under the Home button might be a couple of the other possible causes, either way here are a couple of fixes for you to try out if this is happening to you.
How To Fix:
1. Do a restore from backup
2. Do a clean restore
Those are the first two I would try, or you could simply replace your iPhone or hope that iOS 4.3 can fix this bug.
If you have this problem and know of any more possible fixes for our readers, please tell us in your comments!