I'm getting the same issue!!! Here is my post http://feedback.dayzgame.com/view.php?id=18922

Hello XRW64,

Does this happen on any server that you try to connect to, or is it only specific for some servers? Also, just to make sure, which games have you received the VAC bans for?

Regards,
JStewart

Hello, I was VAC BAN on Call Of Duty, 2 times, and the message appears on all server wen I try to connect

And I Already verify the integrity of the game cache

Then there's nothing that we can do from our end in order to fix it I'm afraid. Since you have not been banned and since there is nothing wrong with your account in the character database, it looks like a local networking issue. For this reason, please refer to the network troubleshooting guide below:

1. Check all the physical devices on your network to ensure they are plugged in and powered on.
2. Perform a connection test on each device connected to the network. For reference, here is a list of platform-specific troubleshooting guides:

http://windows.microsoft.com/en-us/windows/network-connection-problem-help#network-problems=windows-7&v1h=win81tab1&v2h=win7tab1&v3h=winvistatab1&v4h=winxptab1

NAT Types:

• Open
• Moderate
• Strict

Open NATs can connect to any of the three types. --> Probably the least common type
Moderate can only connect to open and moderate. --> Probably the most common type
Strict can ONLY connect to open.
Strict NATs are a difficult problem with peer-to-peer games. Since most people don't have open NATs, the player with a strict NAT won't be able to find many joinable games.

Also, if the player with a strict NAT does manage to join a game, if another player with a moderate NAT joins later, the player with the strict NAT gets kicked out.

Another problem is that sometimes the ISP (Internet Service Provider) is also behind a NAT, which often means even if you have a direct connection to the internet (without a router/firewall), the ISP still acts as a strict NAT.

Port Forwarding:
The following Ports need to be open on your router to connect to the online servers:
TCP 80, UDP 88, UDP 2302, UDP 2314, UDP 2326, 2338

If you need assistance with opening these ports, please refer to the following website for more information (you will need to know your router brand and model, as the website guides are based on specific routers)
http://portforward.com/english/routers/port_forwarding/routerindex.htm

Here are some additional tips that have helped many players improve their connectivity:

1. Make sure your router's firmware is upgraded the latest version (very important).
2. Unplug your router for 10 minutes and plug it back in. Some older routers degrade in performance over time until it is rebooted, similar to a PC.
3. Disable any firewall or other network filtering for the game.
4. Enable uPnP (universal plug and play) on your router.
5. If you don't care about security, enable DMZ (de-militarized zone) on your router for your PC's address. This turns off all of your router's firewall features for that specific PC.
6. Run 'cmd' in administrative mode and use command ipconfig /flushdns
7. Contact your ISP and ask them what your DNS setting should be.

Direct Connection:
If you are still having issues connecting to the online servers after trying the above steps, try connecting your broadband modem directly to the console or PC you are playing the game on. This can help determine if the issue is related directly to the router or another source.

Regards,
JStewart