Could boot from Firewire... Can't now ?!?

[bigbod]

Hi,

I used SuperDuper! to do a full backup of my internal disk (120 Gb) to a Maxtor OneTouch III 500Gb FW400/USB2.0 drive. I tested that I could boot from the Maxtor (no problems).

I then replaced the internal drive with a new 200Gb Seagate 7200.2 drive, and partitioned it using disk utility (GUID).

Now, I cannot boot off the Maxtor. I can select it as the boot drive, but the grey screen icon just eventually changes to a circle\slash icon

Any ideas, I really don't want to pull apart the Macbook Pro again to put back in the old drive.

BTW, I did try a complete install of OS X (Tiger) using the original restore disks, and that worked fine, so I don't think it's an issue with the new internal Seagate drive.

Thanks
Rod