I just got a Western Digital 320 GB MY Book for my MBP. It is taking 20+ minutes to prepare, what is going on? Is this normal? Also its backing up, really really really slow, about 1Kb every 30 seconds, on firewire 800?
The first time you run time machine, it indexes everything on your system. This can take awhile. Subsequent backups should be faster, especially over FW.