Hello,
I don't want to flood this topic but I thought extra info might help. I'm experiencing the same problem on the following machine :
iMac Core2Duo 1.83 GHz, 1 GB RAM
Tiger 10.4.8.
Western Digital MyBook 320 GB, USB 2.0
By the way this is a first backup, not a Smart Update. Both internal and external HDs sound like they're working away, I'm waiting for the process to complete to check if the copy is functional.
Thanks for a great application.