WD My Book Essentials 750GB - Locking up

I lost an external HD in the past and paid to have all our pictures recovered. So I am serious in wanting a reliable backup solution. Here is my setup… I have an Alienware laptop and an ASUS N66 wireless N router with cable modem. I have a WD My Book Live 3TB connected to the router via ethernet. This router also has 2 USB ports. I have the drive listed above and a 500GB version of same thing both connected to the router via the USB ports. I have the drives mapped to my PC. They all show up fine and are accessible until I start copying files to the 750GB. I am using “Mirror Folder” as a backup software solution that runs on a schedule to copy the contents of my laptop to the NAS drive, and then also to mirror the contents of the 500 and 750 USB drives. Whether I am using this software or if I am just copying files in Windows, the blue light on the front stops alternating (indicating drive activity) and I get errors saying the network location is no longer accessible/valid or it will just hang up. It seems worse with larger files (movies). The 500GB gave me a few errors but it copied 147,000 mp3’s and I only had 8 errors. I tried copying some movie files last night and when I checked this morning, 99% gave me the error and did not copy. Yes, I have connected it to my laptop directly and get similar results so it is not the router (brand new btw). It’s like the drive just locks up and freezes and causes the errors when copying. I am not using any WD software on the drives and I have formatted them all to NTFS before use. Any real help would be appreciated.

-Piranha

try testing the drive with chkdsk or Hard Drive Sentinel