I have the same problem as the original poster.
IE9 is already installed and running as expected. However windows update gives the error 9c48 and fails to update.
Downloading and running the offline installer results in an error message stating "setup cannot continue as a newer version of Internet Explorer is installed on your system".
A check show that version 9.0.8112.16421 is installed and is the latest version that I know of.
Any suggestions on how to solve the problem without performing a clean install of Windows 7? Not too keen on doing that.