I played the game just fine for a couple hours straight. For no apparent reason, my connection to the server dropped and I got an error message reading: "The Connection to your Session has Been Lost."

Now I get this message about every five minutes. It's making it impossible to play multiplayer.

Any ideas what's causing it? Again, the game worked fine for a few hours straight, and this happened out of the blue.

bump

I'm getting the same problem! Haven't been able to play a single MP game yet. I don't get this problem with any other MP game and my internet is fine. Anyone have any ideas how to fix this problem?

[edit, bump] This is STILL TRUE FOR VERSION 1.2 patch of Crysis 2 on PC.
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Crytek take note for PC version 1.1 of Crysis 2:

Cannot play multiplayer games, period. Get kicked out of each and every server within 10 seconds of a game starting, no matter what server, what map, what machine or legal copy of the game I am using. Bought a couple of copies, installed on different machines, none work. Single player, no problem... Multiplayer, no way.

First, on a fresh install I get this the very first time I try to play multiplayer:
'Invalid Parameter' in server browser with a fresh install before even getting into the first multiplayer game (after fixing key-stick issue by going Single player then Multiplayer). Looks really bad when the first thing that happens out of the box after you freshly install the game to a new machine and patch to version 1.1 and then run the game for the first time, you're met with a bug. The words "not ready for release" come to mind.

More importantly, I bought a couple of copies of the 'Limited Edition' (haven't gotten to start a multiplayer game in 24 hours so haven't gotten far enough to get any of that either) and am unable to get ANY of them to play a multiplayer game on any machine.

I get disconnected with a "Connection to your multiplayer session has been lost. Please check network connectivity. Returning to Main Menu". This happens when I'm past the lobby in a game map, past the class choice, already spawned, playing on a PC with a fresh install.

Then I sometimes get "The connection to your opponent has been lost. You've been signed out.", sometimes followed by a "Signing out. Please wait." which takes me all the way out to the login screen.

Crysys 2 says I have a "NAT type: moderate".

The 'console' log says...
disconnect cause 11 ... msg "Nub destroyed."

When I get disconnected while in the Lobby waiting for game to start, the console says:
SessionDelete error 0
CryFixedArray removeAt() failed as i=-1 is out of range of curSize 14
Lobby EndTask 18 (18) error 17

Console also says somewhere UserGetPurchaseHistory error 28

another one says
CryFixedArray removeAt() failed as i=-1 is out of range of curSize 15

So, don't know what any of this means. All I know is I bought several copies of the game and they DON'T work, on different machines.
No Multiplayer at all.
I can log-in.
I can see servers.
I can join servers.
But I *ALWAYS* get disconnected.
???

Not good, Crytek. Disabled Microsoft antivirus. No firewall. Still not working. Seems it's Crytek's problem, not the machine.

By the way, on this same network, same PC machines, I can play CoDMW2, CoD Black Ops, L4D2, Bloodline Champions, LoL, Need4Speed, HoN, Team Fortress 2 and dozens of Steam games. What gives?

This is my story EXACTLY. Not a thing is different for you than me.

I just want some answers.

Crytek better fix this **** and fast.

a-men this is my life I've done everything humanly possible to fix the connection issue and nada...

I have the exact same problem! The campaign was incredibly easy so I've tried playing multiplayer pretty much since the release and I've played about 3 full length games so far

this is stupid same happens to me...invalid parameter i mean WTF!!!
campaign=ALL GOOD!!
multiplayer ==NOT ALL GOOD!!!
also whenim playing and i try to join a 15/16 full server it says server full.....
riddled with problems but if they are fixed quickly then ill forgive...;D
Just tell me what to do!!!!!!!!!!!!!!!!!!!!!!