We solved our problem and in the process learned a few things. Thought I'd pass them on in case anyone has a similar issue.
Our issue was that we had a version of java that was incompatible with CodeCollaborator 9
In the $CODE_COLLABORATOR/server/tomcat/logs directory, there's a file called collab.log
There was a Java stack dump in there indicating that we had the wrong version of a library. We updated our version of Java and all was well.
So now I know where to look, and that ccollab depends on Java libraries of version Java 7 for CodeCollaborator 9.