low resolution previews on images only in Acrobat XI?

I have been using Acrobat XI on my Mac Pro running OS X 10.9.5 and suddenly started getting low res previews on images only in all my PDF's.

I upgraded to OSX 10.11.6 last week and the problem still exists.

I am a prepress manager and usually pretty good at figuring this stuff out but this one has me stumped!!

One funny thing i noticed is that if i go into preferences and start changing the settings for resolution i can see the low res previews change to high resolution but the moment i close the preferences window they go right back to low resolution.

HELP!!!