On a similar note... I have a WD drive that has started to click... albeit quite infrequently. It doesn't spin down/up but it is definitely the click of death. I've had no problems with the drive other than the scary click... and running WD diagnostics (a simple and extended test) both passed.
WD are happy for me to return it (it's within warranty)... but do you think they're likely to replace it if it passes their diagnostics (and SMART) tests?? Do you think they're likely to do the same tests, get a pass and send it me back?