Test the following link :

http://{servername} /sdata/{crminstallname}j/sagecrm/-/$schema

If you received an error : Application Error or Runtime.

In IIS,

Activate all the Web Service Extention CGI / ISAPI

Reinstall the CRMRewriter

Open a command Prompt :

go to your Sage CRM Install Dir

cd tomcatbin

Type :
tomcat6 //DS//crmtomcat6

Reinstall : Program Files / IIS Aliases, Reinstall your Patch (SP1, Patch Number …)