MOSS Excel Services – Trusted Data Connection “/” makes the difference
Here is a problem that can be solved in seconds or you can spend few hours trying to solve it and bang your head against the screen (like I did…) when you find how easy is the solution.
I had to configure an Excel service, the Excel file included data connection reference to an MSAS cube. After adding the Excel file, setting the trusted file location, the trusted data location and the security of the data connection, I still got the following error message:
As I said before I did a lot of digging to find out what’s the problem, I repeated the steps above with extra care, and still nothing it took me 2 more rounds of rechecking before I found out that the error was just a little “/” (slash) that was missing in the Trusted Data Connection:
Not Working:
Working:

After that the Excel worked fine and I could drill-down in the cube.
David