Yes, you need to do one of several things:
1. Upgrade to CS5.
2. Use Canon DPP for RAW processing.
3. Download the free converter from Adobe and make DNG files from your RAW, then work with the DNG in CS2 (check that it will work, I'm not certain if CS2 can handle DNG or not).
4. Get a copy of Lightroom 3 and use it to make your RAW conversions, then pass the file off to CS2 for any finishing work.
I use CS5 and Lightroom 3, as well as the current DPP. I shoot RAW almost exclusively and use Lightroom 3 99% of the time for all initial editing of RAW files... then pass off JPEGs or TIFFS or whatever to CS5 for final finishing work.
I have to handle high volumes of images at times, so Lightroom 3 would be my first choice. It's relatively fast and efficient, and dovetails nicely with Photoshop.