Windows and the various Python versions are always ....err.... challenging. In an embedded setup like this, if extensions are build with a different version of Visual C then the python interpreter, it can cause DLL load issues, which might be what we are seeing.
Few ideas:
* Can you look in the windows event log to see what DLL it is failing loading?
* Can you verify which compiler was used to build that version of python by opening up an interactive shell? Should be the first line, or 'sys.version'. Python 2.6's default compiler used VC 2008 (v.1500), which sounds like what you are trying to build against, but maybe they used a newer version to build Maya?
* Did you build the libpq.lib for linking, or was it part of a PostgreSQL distribution? At one time, the PostgreSQL distribution renamed the libpqdll.lib link library to the static version (libpq.lib). Not sure if that is still the case, but it might possible you need to have the libpq.dll placed in the location that the interpreter can find it if you built against a PostgreSQL distribution.
-jason