I was trying to test four modems on a USB Serial Adaptor Friday by using minicom, and had a number of problems that caused minicom to lock up. For some reason, one instance locked and could not be killed, maintaining a lock on the port and occupying the VC it was running on. I eventually rebooted to correct it.
(I eventually figured out that minicom would only address /dev/usb/tts/0, no matter which port I set it to in it's config file.)