I am trying to use the mpdboot command to start 4 processors on which to run my MPI program. I created a mpd.hosts file with 4 nodes (75, 77, 79 and 80). Each of them run python 2.3.4. I also modified the bashrc and cshrc files to ensure that the variables contain the path to the directory of the compiler libraries. I also set up the mpd.conf file and checked that it has rw (600) permissions. 
I have copied below the output screen when I run mpdboot
[n@heart]$ mpdboot -n 4 -r ssh
:38: Deprecation Warning: The popen2 module is deprecated.  Use the subprocess module.
n@75's password:xxx
n@77's password:xxx
n@79's password:xxx
n@80's password:xxx
mpdboot_heart.int(err_exit 526): mpd failed to start correctly on heart.int
reason: 0: invalid port from mpd /opt/intel/mpi/2.0/bin/mpd.py:85: DeprecationWarning: the md5 module is deprecated; use hashlib instead
Killed

PART 2:
I also logged into one of the nodes and tried running mpdboot. Here is the output by doing that
[n@79 ~]$ mpdboot -n 4 -r ssh
n@75's password:xxx
n@77's password:xxx
n@79's password:xxx
n@80's password:xxx
mpdboot_79_0 (mpdboot 499): problem has been detected during mpd(boot) startup at 1 75; output:
Permission denied, please try again.
n@75's password: Permission denied, please try again.
n@77's password: mpdboot_79_0 (mpdboot 515): problem has been detected during mpd(boot) startup at 2 77; output:
Permission denied, please try again.
Permission denied (publickey,gssapi-with-mic,password).
n@77's password: Permission denied, please try again.
Permission denied (publickey,gssapi-with-mic,password).

How should I proceed on this matter?
Is mpdboot compatible with such a version of python? That's downright ancient, I didn't know there was even any distribution left that still shipped 2.3. Have you tried with 2.7?
Mpdboot: Deprecation Warning