thank you for your reply, but this version of Adobe DC being used (along with other adobe packages, as part of the Adobe CC Creative Cloud Suite) is part of a university site licence that we've just started using and at the moment are in no big hurry to change it at the moment.
if you have any other suggestions, or if anyone else has another idea, I'd be greatfull.
Did you ever get this issue resolved? I have a system that is impossible with this error as well.
I have patched, uninstalled, reinstalled, upgraded and done everything I can think of.
Have you tried Adobe's Cleaner tool for Acrobat? Download Adobe Reader and Acrobat Cleaner Tool - Adobe Labs
Any time a plain un-install/re-install does not fix a problem, it may be due to "stuff" that survives an un-install process. The Cleaner will remove anything that is related to Adobe Acrobat or the free Adobe Reader, which means that when you re-install, it is like installing the software for the first time. If is still possible that your problem may not be resolved by the Cleaner, but then at least you know it's not caused by any "crud" that is left on your system.