Minecraft server shuts network down when going into my own server

I can start the server normally, but when my friends or I join the server, it shuts my network down. (I have to reboot my router or wait for 15 minutes to have it back online). It kicks me and says: "Wamzel lost connection: Timed out"

It worked previously just fine.

It doesn't work on bukkit, spiggot or the vanilla servers.