My roadster did this too about 2 weeks ago.
I "cycled" the heating/cooling system. Ran on MAX HOT and FULL FAN for 2 minutes and then MAX COOL (AC) FULL FAN for 2 minutes and it fixed itself. Maybe a sticky damper door someplace?

There is a thread on here (somewhere) also about high cabin humidity. Trying, at 5:30 am, in the dark, at 55 mph to rid yourself of thick inside condensation on the windscreen can be a tad distracting.

If you need your defroster, it seems you must turn on your A/C manually.

When I did this, the mist disappeared as if by magic! Most cars I have owned turn on the A/C automatically to reduce the moisture in the air being blown on your cold windscreen. The (mine at least) Crossfire doesn't seem to do this.

One other thing-how long does it take other folks rear defogger to remove mist from their rear window? Mine takes over 3 minutes to make a couple of lines across the window, and about 10 minutes to clear it.