Before you walk into the store you should try to determine if you're dealing with a compatibility issue or defective hardware. It will strengthen your case if you can narrow it down. Have you tried the Scarlett on a another computer?
If it's a compatibility problem, you can try contacting Focusrite support via email. I did that earlier this year for a bug I found with my Saffire Pro 24. They do respond, but it may take a day or two.