I am using Fedora 16. Using "ls -l /dev/ttyS*" shows 4 "devices" with "crw-rw----" for each one. So then I looked on google for setting serial permissions, and entered "chmod a+rw /dev/ttyS0" as root and the serial port now works! That was a nice victory, but the line must be entered at each boot. (Is there a solution to that?) Thank you, Martin, for the suggestions. I would never have known how to begin to fix the problem.
