If you patch your Arma to the current BETA build, you may not be able to go back. This means all the servers running the official, current release version of the game will not allow you to play, or kick you for missing/corrupt data. "BI Studios is moving into new territory with the BETA's. This means they are departing from where the game structure is, and has been, to a new level. Gone are the days when we can choose to start Arma 2 as itself (v1.60) or as the current dev's BETA Build. The BETA will now, and from now on, need to overwrite core files of the game, and they cannot be reverted without re-installing the game. This means that a copy patched to the most recent BETA is now a different game than Arma 2 was, and cannot ever be Arma 2 again. One thing you can do, albeit rather involved, is a multi-boot OS. If you have room, parse off a partition of HDD space, install Windows on it, and install Arma 2 (and the BETA patch). Keep Arma 2 at v1.60 (current version) on your main boot of Windows, that way you can choose when you turn on your PC which version you want to interact with. Other than that, I can only suggest you wait until they release the BETA as the next official patch. "