From the BBC:
A director at the Large Hadron Collider in Geneva has told BBC News that some mistakes were made in construction.
Dr Steve Myers said these faults will delay the machine reaching its full potential for two years.
The atom smasher will reach world record power later this month at 7 trillion electron volts (TeV).
But the machine must close at the end of 2011 for up to a year for work to make the tunnel safe for proton collisions planned at twice that level.
The machine only recently restarted after being out of action for 14 months following an accident in September 2008.