Well dhouseng, there are numerous possibilites as to the cause of your problem. First let me say that heat from a soldering iron can damage not only the driver board components, but more likely the LED, which generally is more sensitive to heat than the components on the board.
Usually heat damage when swapping LEDs occurs to the LED itself. A lot depends on how hot your iron is, but if you hold the iron to the LED leads/contacts for more then 2-3 seconds (preferably less), the result can be just what you describe. I might add that you need an iron temperature that is "just right" when dealing with these components, I use a 15 watt pencil iron. An iron that is not hot enough will take too long to heat the connection and overheat the surrounding components. An iron that is too hot can, obviously, overheat the components if it is in contact for too long. Between the two extremes however, it's preferable to have an iron that is too hot, as opposed to one that is too cold, that way if you're quick enough, the heat is not a problem.
One other possibility is cold solder joints. A cold solder joint has higher resistance than a nicely flowed joint. This can add enough resistance to cause your problem, as well. If a solder connection is "ball" shaped rather than flattened out, you may have a cold joint.
Dave
