Audition CS5 suddenly can't import wma files

One solution that has worked for other Adobe software when the Dynamic Link server wouldn't open was to trash your Preferences folder, and try again. The simple way to do this is to start Audition with the shift key held down, which will restore vanilla preferences.

There is no guarantee that this will work, but the worst that can happen is that you have to re-establish anything special you had set up. If you are concerned about anything in there, then the safe thing to do is to back up the folders somewhere else so that you can reinstate them if this potential cure doesn't work.