I had the same problem. If I remember correctly, I downloaded the sp1 (not from the update site) then I did a modification to it. I downloaded files to add to it. I burnt onto a cd.Then I was able to install it.Then if you go on the office update page and it comes up that you still don't have the sp1 installed, then you can download it and it will install. Alot of work but that's what you have to do.
Sorry I don't have the link to get these files. Maybe you can do a search here or on www.google.com