Can't Boot from SD clone on LaCie External Drive

[menlomaac]

Dave
This a puzzle. My Mac is an Intel. The drive is LaCie's newest pocket drive (3x5x1/2") called "Little Disk". It has no AC adapter. However, your question made me try some other configurations:
1. I plugged the Little Drive directly into the firewire port of the Macbook. It booted from the Leopard clone.
2. I removed all cables from my MacMini (except the cinema display and USB hub with the keyboard and mouse) and plugged the drive directly into the firewire port. It wouldn't boot up. The screen wouldn't progress beyond the gray Apple logo.
Both my MacBook and MacMini are Intel Core 2 Duos. Why will the Leopard clone boot up from the MacBook but not the MacMini? On my MacMini why will a Leopard clone boot-up from LaCie's older Porsche pocket drive, but not the newer "Little Disk"? Is this a question for LaCie, Apple, or both?
The bottom line is that I need an additional pocket drive (besides the Porshe drive) stored off-site with a Leopard clone that can boot up from my MacMini.