Hello Paul,
Thanks for your reply - it solved the problem!
Or, in fact: there WAS no problem! SP1 had been installed already but without me being aware of it. I never did it myself, maybe it was an auto-update or my Office Package already contained SP1.
Since you told me to look under 'additional version and copyright information' I found the MSO reference there - so SP1 has been installed!
Thanks for the help!
Wim