syfenx... I'm having the same exact problem with the shell I want to use propagating itself over and over endlessly. Did you ever come up with a solution?
In my case I am just running a little exe that launches a couple of executibles and then exits... and that's how I want to use it, I don't want to have to make the shell permanently on.
for anyone that wants to know, i just wrote a batch file that uses the pause command, and turned it into a silent executible file. It launches the program i really want as my shell then just idles in the background. It prevents the endless launching problem.