After doing a lot of tests using both the Mac and PC versions, I think I have managed to identify the cause of the issue. On the MAC version DPP has a problem handling folders with over around 400 images in them. It seems that there is a memory management issue. On the PC version, it does not appear to be a problem.
I run into this often too.
I've also found splitting up my files into groups of less than 300 speeds things up considerably on my i7 iMac and I get fewer DPP-out-of-memory warnings.
I once put over 600 raw + small jpgs from a trip into one folder and DPP basically hung up for minutes and then was extremely unresponsive.
the little I've used DPP on windows it certainly does feel snappier. I don't think the program is making good use of multi-cores/threads on a mac and memory management is less than stellar.
Even Adobe stuff whips large raw images around like nuthin' on my machine while DPP drags along.
Complain to Canon, they sort of fixed a bug I reported with digic 4 based bodies that put a strange kink into the shadow end of thinks causing some strange posterization. Only took about a year.