Debugging MPI Fortran (Linux)

[Carolina]

I'm working with Fortran 77 using LAM-MPI libraries under Linux.
My program (I'm improving tne current version of Xplor by converting
it into an MPI version)has some errors and I want to know where the
error is, I mean, the error's line.
Are there any debuggers that will run with linux fortran? I've already
used gdb
but it doesn't work well.
Thanks in advance.