Can't install Word Viewer

I've recently done a fresh install of Windows 7 x64 Ultimate and am going through installing the software. I've got to MS Word Viewer and it's throwing up error 1406 repeatedly, saying it can't write to Software\Microsoft\11.0\Common\ That key does exist under Current_User but the only thing under it is a key "PersonalMenu", none of the things that the installer is trying to write...