It would give an effect, not necessarily an item that gives an effect. I see you didn't offer an alternative solution. Looks like Pepijn has it covered.
In my experience it is not necessary to set the address in the server.properties, I would suggest resetting it to it's original value. If it worked like this before, or if it still does not work after removing that setting, I would try another port. If another port works, then try restarting your system, this should clear out the blocked port.
What OS are you using? Do you get randomly disconnected from the internet? Have you tried totally resetting MC? Does this happen on all servers for you?
Depending on the Permission plugin you are using, the default group is called "default". Making it to where certain groups do certain things is controlled by permission nodes. Example (perm list for Essentials): http://wiki.ess3.net/wiki/Command_Reference/Perm If you don't have a plugin, I would suggest either PermissionsEx or Essentials GroupManager (but not both at the same time).
FYI that IP (192.168.1.68) is a LAN IP, people can not connect to LAN IPs. You will need to port forward on your router, and then give out your WAN IP, for it to work.