Go to the Adobe website and download the latest Adobe DNG Converter. You want the stand alone converter app.
Download your CR2 files to your computer, then use the converter to convert them to .DNG files. These will then open in Camera Raw.
Hope this helps. The long term solution, of course, is the CS4 upgrade.
How about Lightroom -- will I still need a converter to work on my images in LR?
Thanks, guys! (Even you, Olaf! )