Inspired by some posts in the massive ArtDen DNG4PS-2 thread, I found a solution to my little problem.
As I suspected, the problem was due to the fact that my EXIF data recorded the camera model as Canon DIGITAL IXUS 60, while DNG4PS-2 was expecting a camera called Canon PowerShot SD600.
The solution was quite simple:
In DNG4PS-2 0.2.3-beta12, I clicked on the Settings button and the Camera Options tab. I chose the Canon PowerShot SD600 from the list and clicked the Copy button. This created a new profile called Copy of Canon PowerShot SD600 (which I was not able to rename manually), in the camera name box I typed in the camera name as per my EXIF (Canon DIGITAL IXUS 60) and then clicked OK. I closed and restarted the program. The program at some point renames the new profile to the much more sensible name, and it is able to convert my CRW files. Great!
I hope this helps somebody!