Avid 8.5.3 won't AMA or import ANYTHING!

I have been using MC 8 for ages, numerous projects etc with footage from my Canon 60D. 

Today was the first time trying a new project with 8.5.2 - tried AMAing to Canon footage - get the message that the video is unsupported and I should go to get an AMA driver (these are .mov files). Tried AMAing AVI files - same error. 

Upgraded to 8.5.3 - same problem! 

Please help! 

It gets worse.... 

If I open up an old project (created with 8.5.0) and try to play a previously AMA-linked video (that exhibited no problems in the past) now I get an error 

Exception: A serious error has occurred! 
It is recommended you restart the application immediately. 

If I try to play an AMAed audio file in the same old project, I get 

Exception: Cannot create the AMA sample mapper to play this clip. 

All other transcoded and rendered sequences play fine. 

HELP!!!