The problem was using the option Use J2EE session variables (Server Settings > Memory Variables) in the administrator. Turn it off and all problems are gone. Solved!
I wouldn't really call that a solution. J2EE sessions are important and improve session security as well as a number of other improvements. I cant really see why this option would cause ColdFusion to stop working either, but as you haven't given any errors or explanations of the problem you get, I can't suggest the correct resolution.
You are right. But the solution is OK for me.
But now for all: The problem is (on MAC OS 10.10) turning the option Use J2EE session variables (Server Settings > Memory Variables) in the administrator to on, the ColdFusion 11 Server dosen't restart correctly. It hangs.
I can only access the administrator again (for turning the option off), if I kill the file /applications/ColdFusion11/cfusion/runtime/work/Catalina/localhost/tmp/_axis2/sessions.se r .
After restarting the CF11 server everything is OK (without the option Use J2EE session variables).
And my question again (but now not urgent): Why?
Don't have my Macbook with me at the moment to test but will try later.
I would recommend submitting a bug in case its something Adobe need to fix and are not aware of - https://bugbase.adobe.com/index.cfm?event=newBug