WCF Webservice and SQL Server

I'm building a webservice for use in LAN using WCF. The webservice is using Microsoft SQL Server with a Entity Framework Database and is running using IIS7.

The problem is that other computers in the LAN cannot use methods that return data from the database. If used on the localhost ( while debugging the application) the method works correctly but when used by a remote host ( after publishing the webservice) it returns null.

What could be the problem?

The remote host is getting the error: "The provider did not return a ProviderManifestTok开发者_如何学运维en string."

Edit: I use the IP address of the localhost in the connection string. I added the connection string to IIS.