Don't deal with it. Get a better card for SD capturing.
You have the wrong tool for SD work. HD cards have SD capturing as an afterthought.
You spent ~$300 for HD, so you can probably afford to spend ~$75 for SD. The days of $300+ for SD cards and $1k for HD are behind us. Things are more affordable now.
(Note: I recently listed some ATI 600 USB cards for sale in the marketplace