Can you be more specific?
1) What model of phone are you using?
2) Does the light in the gesture area turn on when you touch it?
3) Did you any recent software changes?
4) Did you make any recent hardware changes?
4) What do you mean by "insertion of phone"?
You can attempt to disassemble and reassemble your phone to find the problem, but I would only try that if you know what you're doing.
IF all else fails, you can try a software workaround and install this:
[App] ButtonRemapper - Beta v0.2.4 (New Galaxy S version added) - xda-developers
Provided your phone is rooted.
It will allow you to map the "Back", "Menu", and "Settings" to your volume keys and camera button.
I used it to turn my volume keys into "Next" and "Previous" buttons for my media player.