You may need to use WDidle3 and disable the intelli park feature to let it boot up. Only Western Digital drives has this.
Original S1 (Recycle Heaven)
Series 2 (PLS, sold)
TiVo HD 1TB (157 HD Hrs, PLS, "652")
Juliet Basic (4XL, PLS)
The TiVo Apocalypse begins on Sat 2013 Feb 16 00:00 GMT!