Black screen for everyone but server owner when people join multiplayer hamachi server?

[BobThePillager]

Me and three friends made a hamachi server last night for Attack of the B-Team, and everything worked just fine. This morning when I rebooted the server, I (the host and owner) could connect and play just fine, but everyone else when joining would see the world like normally for a few seconds, then the screen would go "black" and show the screen that you get when you have gravel fall on you. As this happened, they would sink through the ground until they came out through bedrock and into the void, where they would continue to sink until they logged out. On my screen, they were just standing still, and I could hit them once and it would hurt them on my screen, but they would be ok still. Any further attempts to damage them would not work on my screen either. After them relogging and me hitting them once a few more times, they died. After that, the cool grave thing with all of their items appeared on the ground, and they were met with a respawn screen. When they click respawn, nothing happens. This happens to everyone but me. It worked fine last night, but today we logged on and had to download a few more things from the launch to play (assumably a patch) and I believe that this has broken it. We have tried resetting the server, our computers , everything. Does anyone know how to fix this?

[Kalbintion]

Sounds like a bad internet connection either on their end or the servers end. A minimum of 512kbps upload should be used for small servers. Also, antivirus applications on either end can slow down the connection as it can attempt to read network traffic before allowing it through.