Hey!
 
I am using a Win 7 64bit with the latest Finestra.
 
Whenever I press Alt-Tab to switch windows, regardless whether there is any window open or not (in the screenshot attached, there is no window open on the virtual screen), I get a .Net window in the task switcher (that I have deduced comes from Finestra).
 
I looked through the issue list and I wasn't able to find anything related to this.
 
Please let me know if I can offer more details or can help you test in some way.