Notice a difference? In the first query, I have SupplierID, but the second is SupplierId, with a lower case “d”. These keys are determined when you use sp_set_session_context, which takes a sysname value for the key. These are going to be case sensitive, as each one is a different identifier.
Click through for the full story. I’m not a fan of case-sensitivity in general and especially not in a system where, by default, most things are case-insensitive.