Hovis, no offense, but for anyone capable of reading, you were asking the same question a week ago, in the same thread. And heck, if you scroll back, you'll see I even stated that this is not the first "smoke in cockpit" event that a single operator had to declare an emergency on, on the same type, and on a transatlantic flight.
If you ask me, the question, "is this a common problem?" is the wrong question to ask on a "rumour network".
By definition, no emergency is a common problem. If it were, it either wouldn't be an emergency, someone would issue a fix, or the whole fleet would be grounded until they did. "Common emergencies" just don't bode well for business.
From my experience reading this board, the folks "in the know", (and I sure as hell am not one of them) can provide anecdotal evidence -- what happened in a certain set of circumstances -- and not the quantitative evidence needed to make a judgment such as "this is common". If you want the real dirt, there are plenty of lonely singles in Everett. Hit the weights for a few weeks, go out there, and you'll earn the pulitzer, or whatever it is that's the British equivalent.
Or, if there's an aerospace engineering rumour network, they might know. But I think it's a stretch to have someone say "Yeah, half the time I fly a 777-200, I land with smoke so thick it sets off the aft lav detectors. Thank God for autoland."