Connection problems

Hello,

Before I even start about my problem I'd like to say that I already have done the following:

-disable windows firewall
-disable anti-virus
-Port forwarding
-Disable firewall on the router
-checking logs of the router.

None of it has helped me at all. The following is what happens

I join a game with 6 people inside. I get into the lobb y <5 seconds and here is what I see. I get the pings from 5 people, but one shows 0. When I go to connection info I says the following

*********************

Me
Connected to: Player1, Player2, Player3, Player4, Player5
Attempting to connect to: Player 6

Player1
Connected to: Player2, Player3, Player4, Player5, Player 6, Me

Player2
Connected to: Player1, Player3, Player4, Player5, Player 6, Me

Player3
Connected to: Player2, Player1, Player4, Player5, Player 6, Me

Player4
Connected to: Player2, Player3, Player1, Player5, Player 6, Me

Player5
Connected to: Player2, Player3, Player4, Player1, Player 6, Me

Player6
Connected to: Player2, Player3, Player4, Player5, Player 1, Me

*********************

So it seems that everyone can connect to me and see my ping, but I can't connect to 1 player. Sometimes it's 2.
The logs of my router show no blocked packets.

Anyone has any advise?

The stupid thing is, that before the thursday patch, everything worked just fine.