This is on two Windows 8.1.1 x64 Professional systems with USB 3.0 ports.
Norton Security prevents safely removing a USB 3.0 disk drive (such as a Sandisk Extreme USB 3.0 Flash Drive, a Seagate BUP Fast SSD USB 3.0 drive or a LaCie ThunderBolt USB 3.0 drive) after these drives have been used for activities such as creating a recovery drive, backup copying via Casper Backup copy program or performing other high transfer activities to these USB 3.0 drives.
When I click on the hardware icon in the Notification Tray and select "eject" for the drive, Windows 8.1.1 now finds the drive in use and wants the program that is using it to be shut down. I can wait for over an hour with no activity to the USB drive and it is still found busy. This is 100% repeatable.
This started with NS Beta 1 and was not an issue with NIS 2014.