Apple Remote Access: PowerBook Duo 230 and Error -23

When I use Apple Remote Access (ARA) on my PowerBook 230 with an Express Modem, and I attempt to open a connection; I get the following error message:

"The connection attempt has failed. An unknown error of type -23 has occurred.", or "The connection attempt has failed. An unknown error of type -20 has occurred."

What is causing this?
System 7.5 has the Extensions Manager control panel, which lets a user turn extensions and/or control panels on or off. The Express Modem control panel has been disabled through the Extensions Manager. Enabling the Express Modem control panel and restarting will correct the error.
Published Date: Feb 19, 2012