I sometimes set it to 16bpp to enable screendumps and forget to turn it back...

Best thing to do is to check for a driver update.
If there is none, then file a bugreport to E-Frontier. Since this is a relative new card, P7 might not recognized it and therefore not enable the enhanced features.
You did try the latest Service release 2, I assume?

My experience is that they take these incompatibilities (if that is what they are) very seriously and will seek or provide a solution.

Wim