Ya know - I've had this happen also a few times, but then again, I've been able to disengage it using f12, and also re-engage it. I wonder if it "times" out after being off for awhile.
one thing about track IR that would be nice, bTW would be the ability to have the left right axis reversed when in a dead 6 view.
would a request like that go to the track IR folks or is that something that could be done here?