Just started this behavior in the last week.
Main Evernote window doesn't show the Minimize, Maximize, or Close buttons on upper right, or Explorer bar on bottom of screen.
Other programs behave normally and show these common window manager features. However, if I open a single Note from Evernote, the Note window behaves normally as wel.
I can ALT-TAB to move between programs, but main Evernote window takes up whole screen with no upper right buttons or explorer bar so can't use mouse to move out of Evernote.
Bizzare that only the main Evernote screen does this, and all other open programs, including a Evernote Note in it's own window, behave normally.