If you recently experienced problems downloading content or help files for Revit Building 9. Try again, they have posted a new build that worked fine for me just now. The build number is still 20060619_2300 but the download file has "a" added to it like this:
Revit Series = ARS9_20060619_2300a.exe
Revit Building = RevitBuilding9_20060619_2300a.exe
Download it HERE! Choose your language first.