It appears the recent release of Python 3.0 have a buggy pdb. When I first ran into the issue, I thought it might have had something to do with my unit tests or possible incompatibilities between the subprocess.Popen module and pdb. I wrestled with it before finally throwing a bit of "Google-Fu" at it and discovered that I was not the only person having this issue. (http://bugs.python.org/issue6126)
Python 2.7 is supposed to be a 2.X compatible backport of the features and syntax found in Python 3.0 so any code added to the 2.7 branch must be either a bug fix or a backport of a Python 3.0 feature. Before I learned about that, my proposal was directed towards Python 2.7. The pdb module in Python 2.7 works flawlessly and did not give me any trouble while I was debugging my code with it.
Until the issues with the Python 3.0 pdb module are resolved, I will be taking advantage of the forward compatiblity and coding in Python 2.7 so that I will have a functional code debugger.