Posted 12 April 2012 - 03:27 PM
This is a really common and annoying issue. It is more often a software than a hardware issue.
Mine does this on and off, and as a very temporary solution, something you can do is hold the top button down until the power off message comes on. Then you press the home button firmly. Get back to the home screen and it should work a bit better for a while.
Google 'iphone button not working' and you'll get millions of pages of discussion!