This works if you have messed with your files (Monolingual, XSlimmer), It can't hurt to try it even if you have not run one of these programs.
1) Download the 12.1.1 update directly from Microsoft's Mactopia website.
2) Mount the downloaded DMG file and copy the installer to your desktop.
3) Right-click the installer and select "show package contents"
4) Navigate to Office 2008 12.1.1
Update/Contents/Resources/package_updatable and open the file in TextEdit
5) Scroll to the bottom and find the line "found_valid_version=False"
6) Change False to True
7) Then delete all the text below until the start of "if not
found_valid_version:" Making sure that line is not deleted!
8) Close the window, it will ask if you want to overwrite the file. Say yes.
9) Close the finder window and then run the installer like normal.
10) Reboot.
The first time you open an Office app after this it will take a long time, after that first launch everything should be OK.
The credit for this fix goes to Andrew Murton on the thesource.ofallevil.com forum.
Note: This update does not fix the CGIBitmap error that fills up your logs.