Thanks...I found that it was a problem with PCI probing. According to redhat:
"During PCI probing, Red Hat Enterprise Linux 4 attempts to use information obtained from MCFG (memory-mapped PCI config space ACPI table). On AMD systems, there are buses where this type of access does not work and the kernel cannot parse the MCFG table.
"As a work around, the kernel needs to be informed not to use MCFG on AMD based systems. Use the workaround "pci=conf1" or "pci=nommconf" on the kernel boot line in /etc/grub.conf to tell the kernel to use PCI Conf1 type access instead of MCFG-based access." (http://kbase.redhat.com/faq/FAQ_85_9249.shtm