psycopg2 (and postgres in general) on mac can be tricky. it's been a while since i did this, but the obvious thing to double check is that the web2py is using the same version of python that psycopg2 got installed to. chances are there are multiple python installs on your machine (this is not uncommon) and psycopg2 is not in the same one as web2py is using.
cfh
