You could be getting disconnected for a couple reasons.
1) that zone doesn't work right.
2) your zone servers are set up wrong
3) something amiss with your character.
I've experienced all 3
1) Create a new character in a different zone.
Does it work? If 'No' goto 2.
If 'yes', delete your other characters, and try again.
2) When you run the zone servers make sure the first IP address is your ISP provided IP address. The second IP must be the IP that the world server is running on.
3) Delete you characters and recreate them.
When I had my zone servers misconfgured I was unable to use the characters created with them misconfigured even after I fixed them. I had to delete and start them again.