Player Limits
It was post on the forums that during the downtime Sunday 21st September, they deployed a new feature to Tranquility. The Stargate will now check how many players there are in the system and eve online isk deny access if you attempt to jump into it when too many players are present. In addition to this you will not be able to login on a character if the system has too many players. They have also increased the amount of GMs and if you are unable to login, please press the ESC button and submit a petition in the stuck category.
This is a temporary solution to this issue, they are working on a permanent feature which has the highest priority and will be implemented as soon as possible."