We have the issue with provider worklist at Carle Clinic. I think it is a SQL server bug that involves recording data in the DMVs. Might be a data type issue but I doubt it because other non-uses of indexes due to data-type casting don't show up.

I know that SQL server can only use one nonequality column in a seek. Inequality is any seek that is not for '=' -- '>', '<', NOT IN(), LIKE etc..