I contacted Gerry on skype and it appears that he was able to resolve
the problem by linking his programs to:
/dev/536ep0
instead of
/dev/modem
Apparently /dev/modem does not exist, though it should. If anyone
could take a moment to test this out and report, that would be great.
Just let us know if anything is listed when you run:
ls /dev/modem
Stephen