I recently upgraded to ubuntu 18.04 and using collab client v11.0.11000. When using the client GUI, when adding a new repo, it hangs after clicking on the "Add" Button.
Please try upgrading Collaborator client, as well. You can get its latest installation package from our website.
I'm having the same issue. It also freezes when going to File -> Preferences. Were you able to fix your problem? (Using Ubuntu 18.04 and Collaborator Version 11.3.11301.5)