That was one of our gripes with DPP 4 when it first came out - it wasn't compatible with older (discontinued) bodies. Canon has since added several cameras to the compatibility list, but it's still not compatible with all of them (like DPP 3.x is).

For what it's worth, I still don't use DPP 4 even though my two primary bodies are supported. I found it to be way too buggy in my initial testing. I'm sure it's gotten better since the last update, but I still won't trust it for serious work. Later, I'm sure I will - but not at the moment.

DPP 3.x is still my go-to batch editing program. If I want more functionality, I switch to Lightroom 4.