Yeah, I've found Audition to be an awkward bugger with my newer X-Fi card - it refuses to capture, complaining of mismatched input/output rates (and it doesn't help that setting the card to exclusively output 44.1/16 locks up the system).
Here's what works for me: Capture in Wave Studio > Upsample in iZotope RX > Edit in Audition.
Just letting each app do what it's best at...