I assume you mean the individual channel leds and not the numeric leds.
For the channel leds to shimmer is unusual - I'd try re-flashing the pic before doing anything else. If that doesn't fix it, then you need to post pictures of both sides of the circuit board - especially around the power supply.
The pic output goes through the channel LED and the opto-isolator. If the opto-isolators are installed correctly, the problem goes back to either the pic or the power supply. The triacs attached to the heatsink are connected to the output of the opto-isolator which is there to separate the digital level signals from the AC mains power.
The other things that I can think of that might cause this behavior would at a minumum make something very hot, blow the fuse, or let out some of the magic smoke that all electronics require to operate properly. Let it shimmer for a few seconds, then UNPLUG, UNPLUG, UNPLUG the board and feel the triacs to see if any of them are hot.
Yeah, I said unplug three times with the equivalent of an e-mail shout. If you leave it plugged in, it can bite, hurt, or even kill you, so please unplug it before feeling components with your fingers. There are many places on the board that are connected directly to the hot leg of the AC outlet.
RM