There is a possibility that a process got stuck and you'll need to manually kill it. Activity Monitor is normally a good way to find and kill stuck processes, but the one we're looking for won't show up on Activity Monitor.
You'll need to restart the Mac, but make sure that "Reopen windows when logging back in" is unchecked. If left checked, this can actually restart stuck processes as well as desired apps at the next login.
Or, if you don't want to restart your computer, you can use the Terminal, instead.
Open the Terminal.app in your /Applications/Utilities/ folder. Paste in this command:
ps -cax | grep -i drm
Should give you something similar to:
43964 ?? 0:00.20 DRMWrapper
The number on the left is the application's processID number (yours will be different). You'll use that to kill the stuck process by typing into the Terminal:
(Remember, your DRMWrapper's ProcessID number will be different.)