I have the same problem (and, MS technicians please note, it is nothing to do with my browser cache, my WMP database, or whatever.)
For popular music I almost always have no problem. Where the lookup fails, badly, is classical music, especially box sets. The offered result is quite often wrong, even listing more or less than the number of tracks on the CD. Incorrect performers, incorrect
track titles, even incorrect genres. There seems to be no way to feed back "this is wrong".
The search facility (to try and find a better match) is woefully poor.
I previously used Gracenote (when I had a Creative Zen) and this was right, first time, every time.