I had this problem, also the tool bar very slow to respond. As Media Player is built in, it's hard to fix,If you have more than one account on your computer, does it do the same on them? If not maybe your desktop is corrupt. I solved it by creating a new user account and migrating all my stuff to it then deleting the old account. Nice new media player all working. If you do this make sure you've salvaged everything from your old account like address book,favorites any hidden stuff settings etc. It's not that tricky to do and if your desktop is corrupted probably the easiest to do.