Authentication issues between sharepoint and .Net

[eclipse]

This is kinda hard to explain so I will try and explain as best as I can because Im not sure if this is an IIS issue, a SharePoint issue or a .Net issue. We have an IIS server with a .Net website on there that a user should be able to access data from a SharePoint document library. Ultimately think of the .Net site as an alternative 'front end' to the SharePoint site. The network credentials that the user is using on the .Net site would be the same as the SharePoint site. On the .Net site, the user should be able to see a list of documents from the SharePoint doc lib that they have permission to see. Basically, our setup is (Client)<->(.Net Website)<->(SharePoint doc lib)When we debug the site on our dev computer with the local iis server that runs, we can connect just fine. But when we publish the site to our test IIS server, we get authentication failure when trying to view the page that shows the SP documents. I think we narrowed the issue down to needing either Pass-through authentication or impersonation but we are not completely sure. We tried enabling impersonation but we didn't seem to have any luck and we arent exactly sure about how to use pass-through authentication.Does anyone happen to have any experience with this? Also, let me know if I missed any details. I am not exactly sure what to include.