When openning a network drive, what is the difference between double clicking the driver letter versus typing the letter in address bar then enter? No really you would think.
I was troubleshooting a ticket where a user got "Access Denied" by double clicking in the meantime using address bar worked just fine. Needless to say, permissions are all correct on the netwokr share. It's just how you access it. The issue follows the user so I looked up and down in the user's properties in AD and group policies but failed to find anything.
It turned out it was caused by a little file, autorun.inf, under the root of that network drive. By double clicking the system tried to run it and it required something that this user didn't have permission to. Removing the file resolved the issue!