I'm going to wipe the hard drive, and the re-install everything.
I've been trying to solve a printer issue for a couple of weeks, the printer doesn't work on the iMac but works with no problem on the MacBook. I've uninstalled, re-installed, used App Zapper, repaired permissions, sacrificed live chickens and now I've come to the conclusion that a 'nuke it from orbit' solution is the best.
I'm obviously going to be backing everything thing up onto several different media types before I do this, but are there any subjects that those who have done this before can think of?
Cheers.