interesting that it wasn't a problem until recently. This can sometimes indicate hardware failure, but... Windows Updates and driver updates can make any computer hardware function differently. I've heard of this issue before. It's a power distribution issue and computers are not equal in how this is done. The AudioBox is powered thru USB. Some computers do continue to supply power over USB even when the computer is shut down.
Honestly, using a powered USB hub that has ON/OFF switches for the ports is a very viable solution. I use them myself. Shut Down and flip the switch for your devices. Works fine.