HELP: "Pro Tools hardware is either not installed or used by another program"
 

Am using Pro Tools LE 7.4.2 on my Mac Intel (10.4.8)

It's been running perfectly fine since I purchased them, but for some odd reason, very randomly last night, I tried opening Pro Tools, and right at the end when it's loading all the plug-ins and gets to "Creating DAE Objects," my Pro Tools stops loading and a message appears:

""Pro Tools hardware is either not installed or used by another program."

I click "ok" and Pro Tools completely quits. What just happened? How do I fix this? Any help and advice would be greatly appreciated. Thanks a lot in advance!