did you solve your issue?
I got WDTVLIVE (with up to date official firmware) since many months, working fine with disks of 1 to 2 TB (all WD). Then I bought a 3 TB My Book Essential and it worked OK for a couple of weeks. Then it started to stop playing movies after a few minutes (blocked on an image and after a few minutes, full crash of the WDTVLIVE). Note that these files are played OK on a PC, without any glitch.
Since a few days, the 3TB external harddrive is not recognized any more. It blinks a few time when switched on, but the WD TV Live does not recognize it anymore. I have removed the .wd_tv folder at the root, reset the device to factory settings, but still nothing. My other drives of 1 to 2 TB are still playing fine.
I would continue investigate if someone confirm that My Book Essential 3 TB does work with WD TV Live (as advertise in the compatibility list)