Similar problem happens described by error:
The request filtering module is configured to deny a request where the query string is too long.
Solution, step 1 in web.config:
<configuration> <system.web> <httpRuntime maxQueryStringLength="4096" /> </system.web> </configuration> <!-- OR --> <configuration> <system.webServer> <httpRuntime maxQueryStringLength="4096" /> </system.webServer> </configuration>
Solution, step 2 IIS:
In the Connections pane, go to the connection, site, application, or directory for which you want to modify your request filtering settings.
In the Home pane, double-click Request Filtering.
Click Edit Feature Settings… in the Actions pane.
Specify your options, and then click OK.
Source: Request Limits