Hi,
I had the same problem. Did you try Game Booster ? http://www.iobit.com/gamebooster.html
It has resolved my problem. I had very blurry textures and it happened from day to day...from unknown - for me - reason.
Here are my comments...it's about FSX though, but however it can be applied for P3D too.
http://www.flightsim.com/vbfs/showthread.php?249935-Blurries-long-texture-loading-times-on-high-end-system&p=1730978#post1730978
Hope it could help.
Good luck