Reporting Services Report Server error while installing CRM 2013

Hi All,

We are getting below error while installing the CRM 2013.

Setup failed to validate specified Reporting Services Report Server http://test/reportserver. Error: Unknown exception thrown by report server Client found response content type of '', but expected 'text/xml'. The request failed with an empty response.

Just for information we have NAV installed on same server. 

Can anyone have any idea why we are getting this error. How to resolve it.

Thanks!