Sounds like the game causes a key down event on the Windows key. On my system the game only traps the Windows key (i.e. prevents my use of it), which is very annoying as well.
This is most probably an OS-side problem, and is not client-related. Most probably you or some other program on your OS runs these key-binds. We suggest you to check if there is any third party software installed, that may cause this.
Moreover by default, these bindings open only while windows button is pressed. So we also suggest to check if in any other game you experience the same situation.
ive run through the checks and found that during the loading screen if i use my windows+tab key it will generate the key down event. loading normally and allowing it to start up before switching has fixed it.