Although the Acronis Drive Monitor is a handy tool for keeping taps on your hard drives’ state, it also totally breaks USB 3.0 (at least on my Windows Server 2012).
Acronis Drive Monitor comes with a service called “Acronis Scheduler2 Service”. As long as this service runs, it somehow breaks access to my external USB 3.0 drives. If I try to copy files to my external drive, the progress will freeze after a minute or so (together with a explorer window trying to access the external drive).
Solution: Stop the service (USB drives will start working again immediately), or uninstall Acronis Drive Monitor completely.