I recently upgraded my PGI compiler to version 8, and I had tons of trouble getting the climate model to compile and run. In this case, I decided to switch from mpich 1.2.7 to OpenMPI, on the hopes it would be better for the system and easier to set up.

However, nothing linked properly. If the software compiled, then it would have tons of MPI related errors. As a rule, I install all the libraries needed to run the model in the /opt directory, since it's easier to have more than one version of various libraries (different versions, different compilers, 32 vs 64 bit, etc), so I didn't think there could be a conflict in the libraries.