On Ubuntu karmic with OpenMPI, if nothing is done, then it fails like so:

[pfarrell@saoirse:~]$ python -c "import pypar"
python: symbol lookup error: /usr/lib/openmpi/lib/openmpi/mca_paffinity_linux.so: undefined symbol: mca_base_param_reg_int

As described here, setting an LD_PRELOAD works around this issue:
http://code.google.com/p/petsc4py/issues/detail?id=14

It looks like the author of mpi4py found how to fix this properly later on:
http://petsc.cs.iit.edu/petsc4py/petsc4py-dev/rev/300045797445

Could a similar change be made to pypar?