Type the following in a Terminal window to rename the file -- don't forget to change it back after installation, or Software Update may break (among other things)!
% sudo mv /System/Library/CoreServices/ServerVersion.plist \
/System/Library/CoreServices/ServerVersion.plist.bak
Type your password when prompted, then start the installer. When the install completes, hop back into Terminal and do:
% sudo mv /System/Library/CoreServices/ServerVersion.plist.bak \
/System/Library/CoreServices/ServerVersion.plist
to revert the file back to its original name. Enjoy iLife 04!!!

