Originally Posted by colinm

You should look for a stiff link. Run your finger under the chain while trying to detect a spot that feels stiffer than the rest. Isolate the exact pin that seems tight, there could be several. Grasp the chain with both hands and pretend you are trying to break it, forcing the chain to bend back and forth in the direction it's not supposed to - you're slightly working in the pin, loosening it. Feel again, repeat as necessary.

If you DO break it, SORRY! 1) Not that hard next time and 2) It was a weak link anyway.