Yup...those MyBook drives have been a problem for a while now - and as far as I know, the issues are not related to whether or not the Mac is Intel or PPC. See:
http://lowendmac.com/misc/09mr/mb0429.html among many other references.
This is why I strongly recommend that you/your friend buy a separate internal drive (Western Digital Caviar Blacks, 1TB, remain the highest rated at NewEgg and I have several) and the enclosure of your choice.
If this is a backup drive, rather than one being actively used all the time, I'd suggest saving a pile of money and just getting a USB 2.0 drive enclosure. Firewire is great if you need the speed, but it's certainly not needed for regular backup duties.
This is a good, very reliable option:
http://www.newegg.com/Product/Product.aspx...N82E16817182156If he must have Firewire, then get the Macally or Vantec enclosure. There are 2 Macallys with FW - one has FW400, the other FW800...and costs a lot more.
Pair it with this:
http://www.newegg.com/Product/Product.aspx...N82E16822136284The Samsung 1TB is also highly rated and quite a bit cheaper, but they only offer a 1 year warranty vs. the Caviar Black's 5 years. I'm rather fond of the Caviar Blacks - I have a number of them and none have ever failed on me. I think they're worth the extra $$.
Don't buy stuff like this at a brick and mortar store like Staples or Best Buy or equivalent - they really don't have much to choose from. If you have a computer parts place that has a wide variety of stuff for do-it-yourselfers (like our
http://canadacomputers.com ) then go for it - otherwise, you'll likely do better online at Newegg or Amazon etc.