For someone interested in a small automation of this workaround, I have written a small apple script that toggles between internal speakers and Airplay - taking into account that from time-to-time it is not possible to switch because of the Apple Bug. In this case, the script asks for the Admin password and restarts core audio before continuing.
It is mainly based on the small C program to toggle airplay found here :
http://whoshacks.blogspot.de/2009/01/change-audio-devices-via-shell-script.html
And a proposal applescript that implements it:
http://www.macuser.de/forum/f30/applescript-um-airplay-672797/
Just copy the C programme into the user folder, paste the code below into the AppleScript Editor and save it there as a program.
For me this is working fine and it is much quicker to change to airplay via the dock.