Well it seems like your DB crashes in login. then when you try to login again that session is still active, and hence you get the msg "max sessions". The max session time out is about ~3-5min I think. Trying again after that time will let you login, but in your case it will just crash again and lock you out for another bit.
You need to reinstall your DB, because one of your plugins aint working properly. or something is wrong. Crashes in DB often cause "max sessions" message next time you try to login.