Why do users get a Page cannot be found error when they attempt to change their password in OWA?

In environments where OWA is not installed on the Default Web Site, either the Davex.dll file or the Exprox.dll file intercepts the request and cause a 404 error. To correct this issue, you must remove the inherited file mappings from the IISADMPWD virtual directory properties.

For instructions on how to make this configuration change, refer to https://support.microsoft.com/kb/328242/en-us