I've been using FSX with PMDG and FSUIPC for a couple years, and suddenly, for no apparent reason, I lost the ability to pan the view around.  It just locked up inexplicably.

I have completely reinstalled PMDG, and have deleted FSUIPC from FSX, but the problem persists.  The problem happens in all aircraft, default and add-ons.

My computer is a very high end gaming system, so it certainly cannot be a hardware related problem.  What could possibly be happening?

Hmmm... Actually, it seems like reenabling controllers does the trick.  I don't understand why/how that would help, but I won't question it.

Problem solved...