Linux on Mac Pro

Hi all, Unsure if this is the appropriate forum but since afp548 is on point all the time, I thought it not a bad idea to ask. I am doing a Linux only install on my Mac Pro (dual quad core). After the install finishes and during reboot, I get the question mark folder. My partitions look in order as I use the same partition scheme on all my non Mac boxes. I'm doing a Centos 5.2 Xen kernel install.