Alt-F4 stopped working for me a few days ago, too.

Found that if you right-click on the upper border of that "You need to log in" pop-up window, the context menu which then appears gives you an option to close the window. This has worked for me so far. (Interestingly, the option is described as "Alt-F4" in the context-menu.)

I have not installed any updates since running into the Login problem last year, so I'm curious why the behavior has changed now. The only recent event which comes to mind is that I recently installed Turbo Tax Business, which then accessed the Quickbooks company file to import data. Perhaps it's just a shared function that is used by Intuit apps in common, and a new version came in when I installed the tax app. My trust is now pretty low, however.