I had the blinking LED problem, read this thread and was preparing myself for a large repair bill.
Then I searched the mitsubishi website and found their troubleshooting manual.
I quote: " Why are the 2 lights of the fan coil unit blinking?
They are blinking continuously as the safety switch located on the left of the louvers is not properly locked in. It acts as a safety device and does not mean that your unit is faulty. Ensure that the safety switch is properly secured in position and it will stop blinking. "
Source http://www.mitsubishielectric.com.sg/services-support/faqs
So all I did was to make sure the louvres directing air are properly seated in their places and my aircon worked after that.
Hope that helped