If you run the Oracle Red Hat Compatible 5.10 Xen, and you have more than two option cards in your system, the system might hang or experience poor performance.
Workaround
Add pci=nomsi to the module /vmlinux line in the file /etc/grub.conf:
For example:
module /vmlinuz-2.6-XXX.el5xen ro root=LABEL=/ pci=nosmi