The permission denied problem is caused because you probably forgot to edit the file as root user. When you use knoppix, first of all, you have to switch to superuser (root) in a terminal. Once you did that, you have to mount the fedora partition (e.g. mount /dev/hdc1 /mnt). After that, you can alter the /mnt/etcfstab partition and fix it.
If the mouse pointer hangs, press ALT+CTRL+F1. This will drop you to a command line from where you can change the file with an editor like nano/pico, vi, emacs or using mc.
PS: You posted in the wrong forum-section.