Autopilot problem

For some reason all of a sudden the autopilot ( on any aircraft )will only change the settings for Heading in multiples of 10 degrees or altitude by whole 1000s feet. Does anyone know why this should be and how to get back to where we were before?EDIT( 20 minutes later)- The problem seems to have corrected itself after a couple of restarts of FS9 - nonetheless - does any one have any idea what might be the cause of this?Dave