airsmiles,
ARTCC is an acronym for Air Route Traffic Control Center (spelling of centre intentional because it's an FAA term).
As DaveReidUK pointed out, 7766 is a normal transponder code that is issued an has no relation to an emergency. Just because this specific flight may have had an issue is simply a coincidence. Had they declared an emergency then they would have swapped to one of the emergency codes.
As many of you will know, there are only the three emergency transponder codes (7500, 7600, 7700). There is no mixing of these codes to make a new code - you're either "squawking" one of these codes during an emergency, or you are squawking the code assigned to you by an ATC unit. ATC will not say "ok you're an emergency, here is a hybrid." (The caveat here is that ATC may assign you a new code once you've been identified as the emergency aircraft, as these three codes make A LOT of noise inside an ATC room, but it will not be a hybrid of the emergency codes plus something else).
Now, one does have to pay particular attention when using one of the 75xx, 76xx, or 77xx codes because of their proximity to the emergency codes. It is normal practice to either put the transponder in a standby mode when changing your transponder code (any code) to prevent unintentional selection through the emergency codes, or to change the last two digits first, then to change the first two digits for the same reason.
Hope this helps!