An interesting note this morning, and again I don't know if this is actually an IDLE bug; I had left IDLE running overnight and opened a new code window this morning.  Somehow IDLE "forgot" that Ctrl-N means "next line" and not "new window".  I closed all my firefox windows, then went into IDLE settings, changed the key set to something else and back to Classic Unix, now it works correctly again.

Firefox has been known to steal my keyboard input from time to time when not focused, though it's usually all-or-nothing.  I don't know if it's the culprit or if I'm just blaming it due to past prejudice, but it seems to set things right in IDLE faster if I close all firefox windows.

In any case, I don't know if this could be an IDLE bug or not, just thought I'd share.