I hate to stir up controversy, but in my opinion the reason the original board failed is that Germany doesn't allow lead in the solder, and the original solder is doomed to fail from the beginning. I would (and have) use a solder wick, obtainable at Radio Shack, to remove all the original solder possible, and re-solder the joints using 60/40 solder. (the kind with that nasty lead in it, which keeps the joints from cracking.) An interesting point is that aircraft electronics are exempt from the rule about not using lead in solder. Another way to go would be to use silver solder, which doesn't fail either.

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Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C