Mass duplication of playlists in iTunes

Question

After I set up iTunes Match, iTunes spontaneously created hundreds, possibly thousands of duplicate playlists, all empty.  The number created is so large that it is seriously affecting iTunes performance.  I've no idea how this happened, and am not conscious of having done anything to cause this.  The palylists were just there one day when I switched on.
I've tried deleting, but that is only possible one at a time, and I don't seem to have made any impact on the number.
Anyone know what may have caused this, and/or how to handle it?

Answer 1

My imac, iphone and ipad developed this problem.  Absolutely thousands of empty playlists, all with the same name.  These appeared only when iTunes match was enabled.  I finally got it worked out.  Hoping that this will be of use to others, here's what I did:
1) Turn off itunes match on all i-devices, but left it enabled on the imac.
2) Installed Tracksift on the imac to remove the empty playlists.  It found >11,000!!
3) I left iTunes on overnight hoping that the deletions propagated back to apple's iTunes servers.  I have no idea if this helped.
4) Next day, turned off itunes match and quit itunes.
5) Restarted itunes and turned on match, with fingers crossed that the playlists would not return....
6) Success!  Enabled itunes match on the i-devices.  No more empty playlists, and the proper playlists synced across the computer and i-devices.  Good.
Couple of extra points.  First, several threads suggest that holding the shift key while enabling itunes match keeps the emptly playlists from returning.  Didn't work for me.  Instead, steps 3 - 6 above worked.  Second, I emailed Apple and their rep gave me instructions for removing playlists... one by one.  I appreciate the contact, but not too helpful for 11,000.  Seems that they are not aware of this bug.