Hi,
Ladies and Gentlemen, it seems we have a winner!
Earlier today I was looking at my wife's S5 mini which is fully up-to-date and doesn't have this problem. I tried to extract the CloudAgent app without success, but have since spied post 113 from 'officejudge'. And it seems we have a cure!
Depending on your device and version of Android you may find the widgets to search for have a different name, or simply don't exist. So, try the following:
1. Given your device, go into Settings.
2. Open Application Manager.
3. Select the ALL tab.
4. Scroll to anything that has 'com.sec...' with Knox in the name.
5. Open widgets related to point 4 (Knox) and Force Stop and Clear Data
6. In the Downloaded tab, if you have Security Policy Updates listed then perform a Force Stop too.
7. Now link your Dropbox to your Samsung device, either using My Files, Accounts, or Cloud settings to trigger.
My Note 3 now has Dropbox linked and is now working like before!
Big kudos to 'officejudge' for the Knox update info! So, after all it was a Samsung push which created this problem.
Jonty.