Answered: Cannot create app or Usergroup - Oct. 17, 2012
I have the same problem as described in the previous post labelled "Answered: Cannot create app or Usergroup" dated Aug. 29, 2012
You may need to apply the same solution i.e. please reboot the server.
Solution given for Aug. 29, 2012 identical problem: Yesterday one of the servers failed which caused app/group creation to fail. It was going very slowly, rather than not working at all, so we didn't notice until the evening. I fixed it last night. The next release is built on all new infrastructure, which is much more resilient to failures like these.