Based on news report, its because HKG-FCO flight is delayed 8 hours due to maintenance, hence the delay till next morning.
http://hk.on.cc/hk/bkn/cnt/news/2015...e7f4fac&view=m
But the root of the problem is CX has basically zero spare B77W, as all their aircrafts are allocated to flying nightly. So whenever one plane goes tech, one of their overnight flights will get delayed till next morning. It used to be CX 255 that suffers the most, followed by the Milan CX 233 flight I would say. Like the last time when CX had a plane to LAX grounded in Anchorage, I knew instantly that one of its European flights the next morning would be delayed - and soon enough it was the Milan flight on 31 July that was delayed till the next morning.
Since CX has 19 3-class B77W (according to wiki), utilization as follows
1-2 FCO
3-5 JNB/YVR (CX 838)
6-8 AMS/SFO (CX 830)
9-11 YYZ (CX 826)/LHR (CX 255)
12-14 EWR/LHR (CX 239)
15-17 MAN (DAY 1246)/YYZ (CX 824/828)
18 SYD (CX 139)
19 CDG (CX 279) - Day 146
Add in Sydney and Auckland daily in the winter schedule with B77W and only one extra B77W delivery.
So basically with zero operational spares, there is no choice but to delay selected overnight departures till the morning
Same with the 4-cabins, which CX has 33 of them, which all of them are fully utilized
1-3 ORD/LHR (CX 251)
4-6 FRA/JFK (CX 830)
7-8 CDG
9-10 SFO (CX 872)
11-16 LAX (All four flights)
17-18 BOS (DAY 1246)
19-20 MXP
21-23 LHR (CX 255/253)
24-25 ZRH
26-27 JFK (840)
28-29 JFK (846)
30-31 YVR-JFK (CX 888)
32-33 DUS (DAY 1246 FROM SEPT) and SFO (CX 892 DAY 246)