I googled for a few hours to come up with a very simple solution. I found a lot of pages about the issue, but only one with a solution.
http://lists.freebsd.org/pipermail/free ... 84030.html
http://lists.freebsd.org/pipermail/free ... 84030.html
Code:
aterm
aterm: can't open pseudo-tty
aterm: aborting
kldload pty
solves the issue.