Yosemite: Cannot Music / iTunes - black screen and won't accept password I am trying to open Music. Instead of opening as usual, it does this bizarre slow animated slide-open into a fully black background with a password prompt stating that I've been logged out of iCloud and need to reconnect. See below 



From here, if I try to enter my password, nothing! It won't let me type anything in the field; it will not allow me to cancel; it will not allow me to close without a force quit  as the black screen does not have the normal red close button on top left. I have force quit 3x and tried to start over to no avail. I have done a restart and a hard reboot. Nothing has worked.I just want to play some music. Has anyone seen this? If so, please let me know and if there is something I can do to stop this and open iTunes.

By way of other info:keyboard registering characters everywhere else. It says that my iCloud session has expired, which is why it wants my password, but it hasn't. I went to iCloud through settings and I am logged on. So, while I may have been logged out of iTunes, I am not logged out of iCloud as this states. Lastly, this is a new Macbook; only a month old. I recently signed up for Apple music, but that was 2 weeks ago and has worked fine, so while this may be culprit, it's not been a problem until just now. Just tried getting on iTunes on my phone and i'm on no problem.

Wondering if this could be a virus. Note,the 
"expired session"  message referring to iCloud being logged out does not make since. First off, I am logged in to iCloud Music is not even an affected app as iTunes controls Music.

Ugh!
I'm afraid I've got the same problem.

I restarted the Imac yesterday. The close down took more than 3 minutes. This happend before. I forced the closing down by pressing the power button. After normal start up I could not start iTunes anymore. All other apps function properly. The desktop shifts left and a black screen appears. I can operate the dock and other programms though. I can only get out by forced stop of iTunes.
If I attach my iPhone and start iTunes, a screen prompting me to update it appears (on top of the desktop). I cannot operate it however, as it it is complete dead!

I also tried other option as close full screen, launchpad, ect.

Strange thing is that this occurred about the samen time as my wife synced an iPad which belonged to me before. She was asked to enter ID's of which one was my ID related to buys I suppose. 
I checked my iCloud account. It is still active.

PS!!
I just cracked it! I moved (not copied!) the itunes library to a temp folder.
I restarted iTunes and it immediately came up with the familiar screen. Probably a new library was created. I then imported the info from the temp folder (trough the menu). The new library was updated. I could notice by syncing the iPhone. Also my music is back and available.