Exception when login to the DTR

Hello,

When I try to login to the DTR (at: http://<host>:<port>/dtr) with my User (royc) I receive the following exception:

javax.servlet.ServletException: Group found, but unique name "Technical Services" is not unique!

The stacktrace of this exception keeps prompting this same messege. When I try with other users I am able to login.

Any Idea why?