Problems cased by NIS with JustCloud backup service

I haves used a cloud backup service provided by JustCloud (www.justcloud.com) for a number of years without a problem.  Since September this year NIS suddenly started giving messages that it had removed a threat MyPCBackup from justcloud.exe, including removing all the program files from my computer without warning - this has caused real problems as I have lost my link to the back-up data in the cloud.  Trying to reinstall also gave the same message NIS prevents me from downloading the set-up file.  There are two issues here:  1) Norton's database simply classes MyPCBackup as a 'potentially unwanted app' with a low risk - so why uninstall JustCloud and all associated files without even warning? 2) I contacted JustCloud support and they informed me that their software is virus / malware free and said NIS was giving a false positive and gave me a work around for stopping NIS reacting to JustCloud  which has allowed me reinstall the software and create a new backup on my cloud account.

However, I am not getting repeated warnings each day from NIS that it has blocked an intrusions attempt by 'cnd.backupgrid.net' which looking at the security history shows it is related to attempts by JustCloud to update the desktop backup app which is causing problems as my backup service is reporting that my app needs updating (See attached screen dumps).

I have had two lengthy and very frustrating chats with Norton support who spent several hours running scans to ensure that my system was not infected and making changes to my NIS and uninstalling NIS / reinstalling NIS - all of which simply repeated what I had told them that I had already done.  However, they seemed to be incapable of deviating from a set 'help' script and simply kept repeating what had already not made any difference in the vain hope that something different would happen each time.

Does anybody in the community use JustCloud or had any problems with NIS giving false positives with cloud based backup services or know how I can get NIS to ignore the cnd.backupgrid.net 'attack' so that my desktop app will update? The fact that JustCloud has worked without a problem until September suggests that there is a bug in the NIS database, but I cannot get to talk to anybody at Norton Support beyond 1st tier chat support to report this.  

Anybody any solutions / suggestions?