need help with errors

[$HaDoW]

these errors are killing me !

plz tell me whats the problem and how do I fix it !

1#System.NullReferenceException: Object reference not set to an instance of an object.
   at COServer_Project.DataBase.Authenticate(String UserName, String Password)



2#System.NullReferenceException: Object reference not set to an instance of an object.
   at COServer_Project.World.Chat(Character Char, Int16 ChatType, Byte[] Data, String To, String Message)
   at COServer_Project.Client.GetPacket(Byte[] data)

after error 1 sometimes the player loses it chars !
when I chek the Db the char has no name all stats are 0 !

so whats the problems ???