GODzillaGSPB: I sometimes get this, too. Simply right click on it in the taskbar and select close. Windows will report an application error, just click close again.
No big deal, seems to be a slight bug with the launcher. From all bugs the game could possibly have I'd say this is the least dramatic. :D
predcon: When the Launcher pops up again after exiting the game, even selecting "Close Window" from the taskbar menu doesn't close it. The only way to close it is to forcibly terminate it from the Task Manager.
I see. Well okay then it's a little bit more inconvenient for you I guess, but it's still not gamebreaking.
I'm not trying to cover up the mistakes made by the developers, I'm just trying to be practical. I bet if this is on a "to fix" list at CDPR then it's probably located at the very bottom of it. So I'm afraid we have to live with it at the moment.