Comer
It seems that Cactus doesn't realize that MPI requires a few additional libraries. Most likely, this list of additional libraries varies from system to system, and may depend on the Debian version. Usually, Cactus use shared libraries, and they contain enough information to automatically find and use all necessary dependencies. Apparently you are using static libraries (see "libmpi.a" in the beginning of the error messages), and this requires listing dependencies manually.
I also just see that Cactus build MPI by itself, which it shouldn't have if there is an existing MPI. Also, if Cactus builds MPI, it should have correctly figured out the dependencies! Maybe adding "MPI_DIR = /usr" to the debian.cfg option list would help.
Do you have the output that Cactus produces when configuring? This would tell us why Cactus didn't find Debian's MPI. You could build from scratch, saving all output, and attaching this to a bug report.
-erik