Modem Troubles

Hi. I have a problem with an AOpen modem that is driving me nuts! The problem is that after 1 hour of connection, the modem closes the connection on it’s own. I have looked at the internal Modem settings, System settings and everything I can think of to check. Everything is set so that you have to manually close the connection (NO timeout lengths active).

Would someone here have any suggestions as to what could be the problem(s)?

Thanks you in advance

Earl