This problem is specific to Windows Vista and Windows 7 64-bit.
iPrint client installation fails when installing the client from the IPP page
The iPrint client installation fails when you install the iPrint client from the IPP page using Firefox on a Windows Vista or a Windows 7 64-bit computer.
Firefox does not determine the correct operating system version and it uses the 32-bit client instead of the 64-bit client.
Use Internet Explorer to install the iPrint client from the IPP page.