This bug has been copied from bug #515556 and has been proposed to be backported to 5.5 z-stream (EUS).
in 2.6.18-194.9.1.el5
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2010-0610.html
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: When no hotpluggable PCIe slots were present on a machine, loading the acpiphp module (using the /sbin/modprobe command) on a Intel Xeon processor 7500 series system caused kernel panic. With these updates, an error message is produced when the aforementioned case occurs and the machine does not panic.