As a side note, I've found certain hard drives need a firmware upgrade before they will reliably work with time machine.
This is nothing to do with Apple, but due to the fact that some drive manufacturers enable a sleep mode on their drives.... and hence drives can disconnect from the host computer in the midst of a backup if they suddenly form the opinion that they've been inactive.
PS: What happened to the Mac thread?
Mac users never have any problems, that's why the thread is so quiet.
PPS: There are various esoteric problems with the WD MyBook that require quite a bit of command-line magic to solve. Better solution is to dig out an old PC, and use FreeNAS ( FreeNAS 8 | Storage For Open Source ).
Or you could just buy a better hard drive in the first place....