Using the current stable version of the viewer and host on windows 7, alt tabbing doesn't switch back and forth between the last two most recently used programs. Instead it cycles through all open programs.
Holding down alt while hitting tab multiple times is how you are supposed to tab through all open programs, just hitting alt+tab once should just switch you to the last used window.
Could you please clarify if the issue occurs when cycling through windows on the remote PC or on the local PC? Also, it would be helpful if you could send us a short video. You can send it to firstname.lastname@example.org.