Under the website properties in IIS,

GOTO > Traffic > Filtering

and disable Verify Normalisation.

This setting is preventing your site from displaying pages with escaped characters in the URLs.

Under the website properties in IIS,

GOTO > Traffic > Filtering

and disable Verify Normalisation.

This setting is preventing your site from displaying pages with escaped characters in the URLs.

[update]

In later versions of IIS it is in the general tab of the website properties, and not under Traffic.

Under the website properties in IIS,

GOTO > Traffic > Filtering

and disable Verify Normalisation.

This setting is preventing your site from displaying pages with escaped characters.

Under the website properties in IIS,

GOTO > Traffic > Filtering

and disable Verify Normalisation.

This setting is preventing your site from displaying pages with escaped characters in the URLs.