Sluggish behavior with 1TB Elements drive attached to rear port

My SMP works normally as long as this 2.0 HDD is not attached. Once it has been plugged into either USB port and then mounted, most services become unavailable and general sluggishness ensues. Media library is off. Rebooting without the drive attached and all is well again. I also tried another 1 TB Maxtor USB 2.0 drive with similar results. The SMP will play files from the attached drives without issue. Using 1.09.10 firmware (I haven’t used any other firmware versions). Any thoughts? Thank you

Correction, I can’t get the drive to mount on the front USB port at all.