Flashing Check Engine Light

A flashing CEL is a problem (misfire usually) that has the ability to harm the catalytic converters. If the CEL flashes you need to get to a service shop and have it taken care of right away.

That you have a misfire happening at that time and could damage the cat converter.

A flashing check engine lamp indicates that you have a misfire that's severe enough to damage the catalytic converter. To prevent damage to the catalyst, the car should not be driven until vehicle is repaired.

There ya have it. A catalyst damaging event is presently occurring.
Lets mark this one RESOLVED!