It's just a bad juju after another. Water leaks, alarms going off along the power transmission lines, protesters preventing the government minister from entering the plant by land, and now this.
The Reactor 3 turbine vibrates too much.
From Jiji Tsushin (7/3/2012):
Start of power generation postponed till July 5 at KEPCO Ooi Nuke Plant Reactor 3
Seishu Makino, Senior Vice Minister of Economy, Trade and Industry announced on July 3 that the start of power generation at KEPCO Ooi Nuclear Power Plant Reactor 3 will be postponed until the morning of July 5. It was scheduled in the morning of July 4. According to KEPCO, the vibration of the turbine is exceeding the value recommended by the manufacturer.
UK's Guardian has an AP photograph of protesters and the police and the plant. The final access to the plant by land seems to be through the tunnel.