In Polish:
Awaria Boeinga mog
Data in this article seem to be quite precise, so I suppose it's from reliable source (reference to unofficial information from State Commission on Aircraft Accident Investigation) and worth quoting.
According to the DFDR the failure of C HYD occured just after the retraction of landing gear during departure from Newark, or even at the same time. It's impossible to point the exact moment of failure as this data is recorded only once every 64 seconds. The same minute the gear was retracted there was a sudden drop in hydraulic pressure from 3000 to 400 PSI and 90% of the fluid (3 out of 40 gallons remaining) apparently leaked out to some "hatch" in the aircraft.
Indeed, the circuit breaker had been found tripped by LOT engineers, but it was possible to press it into proper position during the first attempt and that is how the landing gear was extended on ground. Finding out the exact moment when the CB tripped might be tricky (no such data on DFDR), but hopefully entirely possible using the memory of certain individual units (any ideas on this one?).