HELP! Pro Tools 9 Playback Device Issues

Pro Tools 9 is a remarkable leap in Avid’s flagship DAW, but with the new advances come a little confusion and frustration, but FEAR NOT. My hardship is your gain. Is your 002, 003, or Mbox getting the awful error: “Pro Tools could not initialize the current playback device?” Its really annoying and it appears you are completely powerless because you can’t select any options to change anything so you’re stuck right??!!
Not necessarily.
What’s going on is your Pro Tools instance playback device isn’t matching the device settings stored. So how do you fix it?
Very simple. All you have to do is follow these instructions

1. Launch Pro Tools 9
2. When the splash screen appears on the screen, hold down the “n” key on your keyboard, which will eventually open the Playback Engine dialog for Pro Tools.
3. At the top of this window, you will see the ‘Current Engine’ drop-down menu.
4. Choose a different Engine (such as Pro Tools Aggregate I/O)
5. Click OK.
This should allow Pro Tools to launch.
Mac OS X Only
If the solution above fails, you can try deleting the “com.apple.audio.AggregateDevices.plist” preference on Mac OS X. You can find this preference file in the following location:
* Macintosh HD > Library > Preferences
 

If any of these don’t help your problem, you might want to try reinstalling or if you haven’t yet, installing the drivers.
You can find all the drivers HERE
Hope this helps