ASP - Cant open spreadsheet

Hi,
I have an ASP Application. ive just updated one of the pages to read values from a spreadsheet (which is located on a different server).

This works fine on my local pc. As soon as i publish the changes to the production server, it falls over with following error

The Microsoft Jet database engine cannot open the file '\\Server\folder\spreadsheet.xls'. It is already opened exclusively by another user, or you need permission to view its data.

Now this works if i log on to the production server via remote desktop and run the application from there. Just as soon as anything runs it externally it falls over.

IIS is currently set up with just windows authentication.

The account im using to do this definately has access to the folder as its the same account ive used in all these tests and i can open it manually.

This sounds like a security settings in IIS (6.0).

Any idea? Thanks