While the PS3 is switched off, press and hold the power button. As you start pressing, it will beep shorty (as usual). It will again beep after a couple of seconds and then, again, after another couple of seconds. Release the power button and the PS3 will start rebooting.
Have your controller ready and confirm the reboot. It will ask whether to use the friggin’ HDMI connection to drive the TV. Confirm.
After it’s up again, chances are that Minecraft will support multiplayer mode again.
at you own risk …↩