I just bought CS6 and upgraded to Mac 10.8.3. I don't know which is the culprit, but my arrows in Ilustrator will no longer nudge anything. Does anyone have an answer? This is frustrating!
If you have a (reasonable) preference value, it may be worth looking at preferences or disturbance from other applications.
You may try to Move the folder or Other options
Move the folder is reversible (you may also use Ctrl+Alt+Shift/Cmd+Option+Shift during startup, but that is irreversible.
In Other options, the usual suspects are listen in Item 7).