Upgrading ZEN partition to HP6 on Dell 745s

[upinya]

I have a batch of Dell 745s that when I attempt to upgrade the ZEN
Image-Safe Partition from Zenworks 7 SP1 to Zenworks 7 SP1 HP6, I
choose "u" for update ZEN partition, the machine ejects the CD, I
press any key to continue, and the machine freezes. I have to force
the machine off and reboot. When I reboot the machine, it boots to the
updated ZENworks partition, gets to "Configuring lilo to boot to /dev/
sda2" and hangs.

Its the same on every 745 I've tried it on. The same upgrade works
perfectly with Dell 280s and Dell 620s.

Any ideas?