Software Deployment via Group Policy

Hey guys, a colleague and myself are trying to deploy software across a network using group policy. So far all our attempts have been unsuccessful. We aren't sure about what we may be doing wrong. The MSI package is there and ready to be deployed, and as far as we know the permissions are correct--yet I can't help feeling the problem is going to be with permissions. Another thing which I have a horrible feeling about is when we create the package and tell group policy where to find it, it says that it can't verify the source. :confused Any help or direction will be great!