2003 admin install + sp1 = "not entered a valid product key"

I have a 2003 administrative install from which I have been installing Office 2003 via GPO with no
problems (albeit with an mst which includes the product key). When I attempt to apply SP1 to this
admin point I get the error "you have not entered a valid product key" and the SP1 setup fails. How
do I rectify this?

More info-

command line syntax-
Z:\msiexec.exe /p
\\server-beta\files\office2003sp1-kb842532-fullfile-enu\mainsp1ff.msp /a
\\server-beta\public\office11\pro11.msi /lv* sp1.log

relevant error from the installer log file-
MSI (s) (58:68) [13:48:50:965]: Doing action: SkuredPidkey
Action 13:48:50: SkuredPidkey.
Action start 13:48:50: SkuredPidkey.
MSI (s) (58:68) [13:48:50:996]: Transforming table CustomAction.

MSI (s) (58:68) [13:48:50:996]: Transforming table CustomAction.

MSI (s) (58:68) [13:48:50:996]: Note: 1: 2262 2: CustomAction 3: -2147287038
MSI (c) (04:AC) [13:48:51:006]: Transforming table Binary.

MSI (c) (04:AC) [13:48:51:026]: Transforming table Binary.

MSI (c) (04:AC) [13:48:51:026]: Note: 1: 2262 2: Binary 3: -2147287038
You have not entered a valid Product Key.

Please check the number located on the sticker on the back of the CD case or
on your Certificate of Authenticity.
MSI (s) (58:68) [13:49:51:492]: Product: Microsoft Office Professional
Edition 2003 -- You have not entered a valid Product Key.

Please check the number located on the sticker on the back of the CD case or
on your Certificate of Authenticity.

That's kind of what I was thinking- that I had to rebuild the AIP. The reason for the .mst is for
customizing the rest of the install, I was just noting that the PID was contained in the .mst as
well so maybe that's why I have been able to deploy via GPO without issue even if the AIP was
missing the PID for some reason.

I'm sure I had to specify the PID when I built the AIP initially, however, but it's been quite a
while...