This is all I have in my Ubunto setup:
export GLADE_HOME=/home/keith/glade4_linux32_ub10
export PATH=$GLADE_HOME/bin:$PATH
export LD_LIBRARY_PATH=$GLADE_HOME/lib:$LD_LIBRARY_PATH
export PYTHONPATH=$PYTHONPATH:$GLADE_HOME/bin
export PYTHONHOME=/opt/ActivePython-2.7
From the Python documentation, modules are searched according to PYTHONPATH:
When a module named spam is imported, the interpreter searches for a
file named spam.py in the directory containing the input script and
then in the list of directories specified by the environment variable
PYTHONPATH. This has the same syntax as the shell variable
PATH, that is, a list of directory names. When PYTHONPATH
is not set, or when the file is not found there, the search continues in an
installation-dependent default path; on Unix, this is usually
.:/usr/local/lib/python.
It looks like you need to change your PYTHONPATH so Python can find the site module.
For example, mine is at /opt/ActivePython-2.7/lib/python2.7/site.py