We recently acquired and installed Nevron Charts for SharePoint 2010.

When I try to connect to an Excel workbook I get an error:
Error: Cannot connect to data source.  Error was:Exception has been thrown by the target of an invocation.

This is what I did to get to that point.

1. I added a nevron chart web part to a page.

2. In the configuration I put a link to my excel file that I want to reference (http://mysite.com/Shared%20Documents/test.xlsx)

3. Put in the range (A2:B54)

I had a rather involved spreadsheet with a lot of calculations and data and thought maybe I was trying to reference to much so I created a simple sheet with a date column and a currency column and pasted simple values in and saved it as test.xlsx and still no joy. The document is checked in, published as a major version and I am able to view it in excel services in the browser.

PS. The WYSIWYG tools on the forum here seem to be inop, using IE8.