Some software, such as fax modem software, will put the modem into auto-answer mode. The modem may have to be considered busy while the modem listens for an incoming call. This can happen with a background process or a system extension, in which case there doesn't have to be an open application. Launch your software and check the setup controls to see if auto-answer is on. For example, if there's a control for Answer on <3> rings, you might have to temporarily turn the modem software off or set it to Answer on to free up and then eject the modem. Refer to the users guide which came with your modem software for more information.