a,
It is the top subject in the forum right now, and our staff friends are working on it.
The (main) cause is the use of multiple montors, but unplugging one/more is hardly a good cure.
You may get round it following the procedure described in post #24 by kdsi elaborating on post #20 by James in this thread,
https://forums.adobe.com/message/8092176#8092176
getting rid of the offending file called WSMgrCfg in the folder WSMgrCfg (same name).