I have uploaded an xlsx file that I would like to use EWA to display using Excel Web Services. I have confirmed that the site is a trusted location and Excel Web Services is configured correctly from Central Admin. A simple spreadsheet works fine and renders in browser. However, for one particular worksheet I get an error when I try to point the EWA web part to it. It is indicating that it contains the following features that are unsupported by Excel Services. The error references sharepoint lists as the feature not supported. What is SharePoint Lists referring to? I removed the data connection that existed in the workbook but that still didn't work.
If I am not mistaken you cannot use a SharePoint list as a datasource in an Excel sheet which in turn is displayed as a web drawing. Now with SP2010 there are ways to work around this:
Microsoft SQL Server 2008 R2 PowerPivot for Microsoft Excel 2010
User-defined functions (UDFs)
Web Services API
Java Script Object Model (JSOM)
But because your tag is SP2007 I am afraid it won't work.