partition types on on iMac

Hello, I'm trying to install 10.0 on my iMac but the install fails when it tries to format my partitions - it says it can't change the type. I partitioned using pdisk under OSX, and I've tried marking the partitions as "Linux" and "Linux swap" but to no avail (not using the hex numbers, just the descriptions) . The install fails when it tries to format the swap partition. pdisk from the suse disks wouldn't let me change the type, and pdisk on the mac wouldn't let me write the partition table! Anybody come across this or have ant suggestions? Thanks, Chris