I recently purchased two Lacie 2 terrabyte USB 2 drives and had difficulty formatting them on my Macbook Pro, Leopard, OS 10.5.8. Then I found the answer:
Fantastic, this finally gave me the answer I was looking for, after whole 2 minutes of thinking and 10 seconds of searching.
Just for clarification reasons: click on the line of the drive, not the partition, and click the tab “Partition”, then look on the bottom for “Options”, click that, and do as he explained (select GUID for Intel Macs).
To see the entire thread, follow this link.