HI HomerJ,
Usually when the issue arise like this, it can be attributed to a bad temporary folder (the TD_80) folder. Within the temporary folder are stored the temporary settings as they pertain to the user account on the local system, it is essentially a cache of system and environment settings at they relate to the user.
You could try first to remove the TD_80 folder (don't worry it will be rebuilt/ recreated again the next time that the client is entered). To remove this folder you would need to open file/ Windows Explorer and then within the navigation bar type %temp% and hit enter. This will navigate to the temporary folder where the TD_80 is found, Scroll down and find the TD_80 folder and delta it. This should hopefully resolve your issue.
If this doesn't work you may have to try to delete the client entirely from the system and reinstall it. You should contact your QC Admin and they should be able to get you a copy of the uninstaller to make this an easier procedure or they can get you a copy of the manual uninstall procedure to follow.
I hope this helps resolve the issue.
Dan