Marco

If you only have 1120 rows, it may be that the query optimzer decides that it's better to do a clustered index scan than to use the index. I don't know on what basis it overrules index hints, nor whether that is even documented. I'd be surprised if the failure to use the index is the reason for the drop in performance. If you post the execution plan, we can have a look and see whether there are any clues.

John