If you casually update with 6 updater like me, you may find yourself with a problem. The latest beta patches update the game and/or battleeye to version 1.61. It's all changes relating to the Army of the Czech Republic addon and will give us ACR lite with the next game update. All good stuff, but what isn't explained is that while you update to game version 1.61 nearly all the servers will still be on 1.60 and you will not be able to connect. You will notice that the majority of servers will have a red X icon next to them. Upon joining the server you will be kicked with a "Failed to connect" error message.
Deleting the beta folder will not solve the problem as battleeye is also changed. You will have to reinstall that as well. If you also download the ARMA 2: OA 1.61 (Release Candidate #2) build 95054 you will be totally screwed and require a full game re-install, so especially don't do that without reading the smallprint. It is in the beta forum section and looks almost like a beta patch, installs the same way, but it isn't. It permanently changes the game. You have been warned!:
-Don't apply the latest beta patch with 6 updater until your favourite server has also done so.
-Don't install the 1.61 update release candidates unless you really want to, it can't be undone without a full re-install.