Do you just want to debug plain old C++ code w/o debugging the Python code or were you wanting to debug both together? I've opened a feature for the latter (http://pytools.codeplex.com/workitem/210)
if that's what you want but we won't be able to get to that soon. Either way I think this will need VS Pro or above as I don't believe the integrated shell includes native debugging.
If you just want plain old C++ debugging I would recommend:
A) Make sure you attach w/ the correct kind of debug engine (select Native in the "Attach to:" area of the attach to process dialog)
B) Make sure you can successfully load the symbols. You can look at the Debug->Windows->Modules to see the list of loaded modules, the status of their symbols, and even to load the symbols for a specific module. If the
symbols aren't found you'll be prompted to point it at a symbol file.