For a long time I have been having a problem playing CDs from WMP Series 9. I believe this was because of a conflict with a DVD Program, but I also noticed that others have / had the same problem. Issue solved... delete CD rom specs from this folder:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\MediaResources\mci
I had this same problem. I ended up getting Music Match Jukebox because I was tired of trying to figure it out. I had no other dvd program at the time so I knew it was a problem with the new WMP release. I never had this problem with 8, but in started immediately when downloading 9.