USB 3.0 HDD won't stay connected; FNet Turbo HDD USB won't detect it

I just bought a new Western Digital Green 3TB hard drive, WD30EZRX, and a Connectland external enclosure, CL-ENC35020. I had quite a bit of trouble getting anything to detect the drive first off, *but I finally got it initiated, assigned a letter (M), and formatted it to NTFS.* (It's for Movies, and no Macs here.) *But now, when I try to copy my movies from my regular data drive (D), it cuts...