Like I said, chown -R 777 *

Perhaps you set the folder to 777, but not the files inside it.
To be honest now, I'm now not sure what happened. I managed to borrow a couple of SATA drives to try to replicate the problem, and of course I could not.
I Just could not replicate the same conditions. For example I could not get to a state where I could add a file or directory, but then could not delete it. All I could manage to do was to have no ability to do anything other than read it, which is what should happen. I didn't even try creating the situation where I had full access if it was mapped to a drive letter, but had problems if it was referenced by the UNC name.
As soon as I experienced unexpainable symptoms, I should have reset to defaults and reboot the NAS. After reading the forums that solution seems to fix a lot of problems.

Z