Design editor not opening in RH9

I've been having various problems with RoboHelp 9 lately, most of them now solved.  One still remains, however.

In my user account, the design editor won't open for our own projects (it does open for RH's demo projects).  Since it works fine in my admin account, I thought it was a rights issue, but I've given "everyone" full rights, and it's still happening.

I've tried renaming the .cpd file, but that didn't help.

Trying to fix the other problems meant giving Adobe access to my system and letting them fiddle with the registry and reinstalling programs.  (RH9 has been uninstalled and re-installed.)  My RoboHelp is part of the TCS, which doesn't help.

Does anyone have any suggestions? 

Thanks.

Marion