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.
As it turned out, however, one of the MPI solutions still was getting installed in the /usr directory. On a mac, this can be a big problem because the macos goes for dynamic libraries in the usual places before loading anything in /opt. Hence, I was compiling for OpenMPI, but the OS was loading either mpich, OpenMPI without fortran support, or 32 bit instead of 64. The results of which are not pleasant.
The upshot to solving this problem is that I might be able to get the GCC/g95 solution to run the model instead of the Portland compilers. I'm happy with the portland compilers, but they're expensive to keep current. So, it's time to give it another go!