All USB ports unresponsive, Internal and Exernal

Exactly as the title says, on my MacBook (Late 2007 2.2ghz, 4gb RAM, 500 GB HDD) all the USB ports are unresponsive, but only within OS X. I can do the various boot up commands, and the keyboard and mouse work their, but within OS X, they do not. I have a bootable backup, in which the USB ports do work though, so this is a software issue rather than a hardware issue. I want to try and avoid reinstalling OS X, but I am afraid it may come to that.

Ok, I archived and installed and everything is back to normal.