[eluser]xwero[/eluser]
Do you upload your xls in the same directory as where you tested your own uploaded xls file?
I get excel data from an uploaded xls file just fine.
I remember i had to add a mime type to the xls key in config/mimes.php because when it was uploaded with IE it has a 'application/octet-stream' type.
And to be sure you should check if the xls is uploaded properly.