in kernel-2.6.18-164.2.1.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-2009-1455.html

Updated from the customer.
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Latest test using RHEL 5.4 with no modified rpm's  
kernel-2.6.18.164.2.1.el5
device-mapper-multipath-0.4.7-30.el5_4.2
kpartx-0.4.7-30.el5_4.2

multipath -ll -v2 returns expected result.
dd if=/dev/zero of=/mountpoint dumps data at expected speed.

Non modified initrd causes so many errors that it slows up the boot by four and a half minutes, when compared to running modified initrd:
mkinitrd -f /boot/initrd-$(uname -r).img $(uname -r) --preload=scsi_dh_rdac  
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