I was logged on and the connection to the Internet/chat server dropped. I cannot log back with the same username (nick) Why?
If you log back via the same machine (IP address) it detects a more recent login and lets you in. However if you use another IP address (another machine or a dynamic IP address), it will not permit another login if it still has a login under that user name. After a time-out period of 10 min the user is automatically logged off and you can then reuse the same user name (nick).