in case anyone else should encounter this problem, i got infected with it today and spent 8 hours pulling out my hair and screaming at the wall and trying all the troubleshooting suggestions above to no avail, until i finally noticed this one little question from avid tech support above that i had somehow missed the first 30 times i read through this thread:
<<Are you making sure to have the 002 on before you boot up your computer?>>
i don't recall ever having to do that before! but i did it tonight and, voila, everything is perfect. my digi002 is no longer grayed out in my audio midi setup window, and my protools and my digi002 and my midi controller are all talking to each other again as if nothing was ever wrong.
phew.
so, in short: turn on your 002 before you turn on your computer!