So me and my friends downloaded a custom map to our bukkitGUI server. I have no plugins because we do survival multiplayer on it and we dont need plugins. About every 5 minutes my server freezes and we all assume its going to crash. It does. When I look at the chat log it says:[WARNING] Can't keep up! Did the system time change, or is the server overloaded? Is it because I'm running a 1.6.4 server? (because of the map version) Or no plugins? My friends get really mad because of the server crashing whenever it says that. it's really bothering me and I wish I could just play on my server without having to restart the server every 5 mins! Someone please help!