Unfortunatly cs4 does not support the required camera raw plugin 6.7 that you would need.
Photoshop cs4 only supports up to the camera raw 5.7 plugin.
Two alternatives would be using the 7.3 DNG Converter to convert your files to dng copies which then photoshop cs4 could convert to jpegs or using the canon
software to convert the camera raw files to jpegs or tiffs if you want to edit them in photoshop before saving as jpegs.
What operating system are you using?
Thread moved from PS Beginners forum to Camera Raw fourm.
In lieu of upgrading Photoshop to the current version, you could also get the current version of Lightroom 4.3 which is much cheaper than Photoshop, and use that as the raw-adjustment front end to the older Photoshop, via LR’s Edit in Photoshop with Lightroom Adjustments. You would want to try the Trial version of LR to make sure it can run well enough on your computer.