You cannot load an Excel 2007 workbook in Excel Web Access when a SharePoint Server 2007 Web site uses Basic authentication and when the trusted file location type is set to HTTP

Consider the following scenario. You have a Microsoft Office SharePoint Server 2007 Web site that is configured to use only Basic authentication. Additionally, you have an Excel Services trusted file location that has the location type set to HTTP. In this scenario, when you try to load an Excel 2007 workbook in Excel Web Access from the trusted file location, you receive the following error message:

When an Excel Services trusted file location has a location type of HTTP, Excel Calculation Services (ECS) uses the WebDAV protocol to obtain the document. When only Basic authentication is enabled, ECS cannot access the document by using WebDAV. Therefore, you receive the error message that is mentioned in the "Symptoms" section.

This behavior is by design.

ECS uses one of the following three methods to obtain files that are in a trusted file location:

• Microsoft Windows SharePoint Services
• UNC
• HTTP (WebDAV)

For UNC and HTTP, there are two ways that ECS can use credentials to access files. ECS can impersonate the end-user. Alternatively, ECS can use the ECS process account. If ECS impersonates the end-user, Kerberos is required because ECS delegates the user identity. If ECS uses the ECS process account, Kerberos is not required because ECS uses Windows authentication (NTLM) instead.

ECS does not support Basic authentication when it is used together with HTTP. ECS supports only Integrated authentication in this scenario. As previously mentioned, Kerberos may also be required in this scenario, depending on your configuration.