Nope.

I think it's a driver issue. After posting the question, I imaged my iATKOS 5i DVD onto the USB drive and was able to boot it as the installer.

The question now is which driver is it.

---

Mac OS X Leopard 10.5.7 (Retail)
Motherboard: MSI P6N Diamond
Processor: Intel Core 2 Quad Q6600 2.4GHz
Video Card: MSI NX 6600 TD256E (CI QE Dual Displays)
Memory: Corsair TWIN2X4096-6400C5DHX 4GB DDR2