LAM: Mac OS X heterogeneous cluster mpirun problem

Hello LAM/MPIers:

I have compiled the Gromacs MD program for both PPC and Intel, I can run each binary on their corresponding architectures, but when I try to do an mpirun across the two different machines, the job fails after a few seconds. Each machine can see and execute its architecture specific binary, the LAM/MPI is the universal build of LAM/MPI 7.1.2 from the website. Any ideas on what I might be doing wrong? Below is the only message that I'm getting:

calculon$ mpirun -np 4 mdrun

NNODES=4, MYRANK=1, HOSTNAME=Warner-Computer.local

NNODES=4, MYRANK=3, HOSTNAME=Warner-Computer.local

NNODES=4, MYRANK=0, HOSTNAME=portal.private

NNODES=4, MYRANK=2, HOSTNAME=portal.private

NODEID=2 argc=1

NODEID=0 argc=1

NODEID=1 argc=16777216

NODEID=3 argc=16777216

MPI_Recv: message truncated (rank 2, MPI_COMM_WORLD)

Rank (2, MPI_COMM_WORLD): Call stack within LAM:

Rank (2, MPI_COMM_WORLD):  - MPI_Recv()

Rank (2, MPI_COMM_WORLD):  - main()

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One of the processes started by mpirun has exited with a nonzero exit

code.  This typically indicates that the process finished in error.

If your process did not finish in error, be sure to include a "return

0" or "exit(0)" in your C code before exiting the application.

PID 341 failed on node n0 (10.0.1.1) with exit status 1.

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