When trying to open a excel file many come across this exception stating :
"The workbook that you selected cannot be loaded because it contains the following features are not supported by Excel Services"
Many blog suggested for Excel Services Trusted Site Entry for the excel file referring.
However the solution that worked for me:
Give "Read permissions" to the users and they will be able to open the file using excel client.
For more info on how to see permissions you have for users and groups in your site go to: Site Actions > Site Settings > Advanced Permissions.
Edit User Permissions to Read
Also make sure the permission are inherited to the Document Library permissions.
Revert with your Comments on the same.