That's definitely a long string! You can try clearing your browser cookies. Even though it's not an elegant solution it can work as a temporary workaround.
Ideally if there's a way to redo the logic to issue a shorter request, that would resolve this.
You could add a limitation to your web.config:
<system.webServer>
<security>
<requestFiltering>
<requestLimits maxQueryString="32768"/>
</requestFiltering>
</security>
</system.webServer>
http://www.iis.net/ConfigReference/system.webServer/security/requestFiltering/requestLimits
And:
<httpRuntime maxQueryStringLength="32768" maxUrlLength="65536"/>
(Max length numbers are just examples.)