Woah.. That looks amazingly and awfully wrong.
Put that back to 10000-20000. There's no reason to change it, unless you have another SIP server behind the same firewall. And if you have two sip servers behind the same firewall, you're going to be having strange and awful problems like you are now.
Edit: You also should not be using STUN or anything, if you're on the same network segment. Maybe you should just reset your phone to defaults, add the extension back in and don't change anything else and see if that fixes the problem.