Here is the problem in a nutshell: An editor opens the category tree, finds a link, clicks "Edit", makes a change and clicks "Modify Link". The screen closes as normal and the system displays "Link Modified Successfully". If the editor then clicks on "Edit" again, the change he has just made does not show. It has in fact been recorded in the database, but it does not show on the editor screen.

Can anyone point to the likely cause of this?

In the Admin tree on the same GLinks installation we get normal operation, no problems.
In the Editor tree and the Admin tree of a different GLinks installation on the same website/server we also get normal operation.
This suggests to me that there is some misconfiguration of the installation.

Also, is it possible that the dreaded "Rebuild Category Tree" would help here?

Thanks,
--Jo