Synchronisation stopped at one specific blockchain

Question

I've successfully been using Bitcoin core for the past months, but since two weeks ago its synchronisation is always stopped at the exact same blockchain. 2 weeks later, sync is behind by 2 weeks. And the error message is still the same: "No block source available" and I have 0 active connections to Bitcoin network.

I have updated the client, and changed networks (I even tried from another country to tell you the truth). I tried to type in "rescan" and "reindex". EDIT : they worked, but sync is now stopped at another block...

Here is the end of the debug window after I did a rescan :

2016-12-25 21:36:12 Still rescanning. At block 440686. Progress=0.988020

2016-12-25 21:36:53 rescan 821342ms

2016-12-25 21:36:54 mapBlockIndex.size() = 441449

2016-12-25 21:36:54 nBestHeight = 441448

2016-12-25 21:36:54 setKeyPool.size() = 100

2016-12-25 21:36:54 mapWallet.size() = 6

2016-12-25 21:36:54 mapAddressBook.size() = 10

2016-12-25 21:36:54 init message: Chargement des adresses...

2016-12-25 21:36:54 torcontrol thread start

2016-12-25 21:36:54 Loaded 60362 addresses from peers.dat 457ms

2016-12-25 21:36:54 init message: Chargement de la liste d'interdiction...

2016-12-25 21:36:54 init message: Starting network threads...

2016-12-25 21:36:54 AddLocal([2a01:cb00:b1d:1d00:7f:42c7:afca:6f9a]:8333,1)

2016-12-25 21:36:54 Discover: ASUS-PC - 2a01:cb00:b1d:1d00:7f:42c7:afca:6f9a

2016-12-25 21:36:54 AddLocal([2a01:cb00:b1d:1d00:d8e0:fea5:2db:481f]:8333,1)

2016-12-25 21:36:54 Discover: ASUS-PC - 2a01:cb00:b1d:1d00:d8e0:fea5:2db:481f

2016-12-25 21:36:54 dnsseed thread start

2016-12-25 21:36:54 net thread start

2016-12-25 21:36:54 addcon thread start

2016-12-25 21:36:54 opencon thread start

2016-12-25 21:36:54 msghand thread start

2016-12-25 21:36:54 init message: Chargement terminé

2016-12-25 21:36:54 GUI: Platform customization: "windows"

2016-12-25 21:36:54 GUI: PaymentServer::LoadRootCAs: Loaded 44 root certificates

2016-12-25 21:37:05 Loading addresses from DNS seeds (could take a while)

2016-12-25 21:37:05 0 addresses found from DNS seeds

2016-12-25 21:37:05 dnsseed thread exit

Any leads ?