Let me tell you a little story:
A long time ago a stupid teenager buyed Arma 2 Combined operations on Steam and he thought it will be funny to hack in dayz, he spawned Weapons and Cars and ported himself whereever he want. And then he got banned with the next Battleeye Update. He was sad and flamed, but then he go to the next Gamestop and buyed a new key. He changed the keys via Regedit.exe and started arma via Arma 2 Launcher and again he could play whatever he want, just without hacks , he played and played but then Gamespy Bohemia dropped Gamespy and he cant play Dayz over Arma2launcher anymore. He started Arma 2 over steam and tryed to get on a server but he is banned. He thought why i get banned and look over regedit.exe that Steam changed the key and that Steam change everytime the Key when he Starts Arma2. Sad and helpless he goes to a forum called https://forum.originsmod.info and asked there hopefully for help... And now the suprise. The Guy is in reality me
the End...?

From the battleye page:

Sudden global bans after latest BE update - 15.07.2014 • 13:10 wrote:Certain users have been contacting us regarding sudden global bans since last night when a BE Client and Server update was released for ArmA 2: Operation Arrowhead. To clarify, these bans are not false positives in any way.

In reality these are bans from the past that are related to the cd-key that is attached to a user's Steam account. Yesterday's update added support for old cd-key-based global bans in the new Steam version of the game (1.63). Note that with Steam the cd-key that is written to your registry is no longer relevant for authentication. Only the cd-key that is attached to your Steam account matters and like in previous game versions you will not be able to play on BE servers with a cd-key that is globally banned.

Therefore, if you previously had been using a new unbanned cd-key by writing it directly to the registry you will now have to attach it to a new Steam account to be able to play on BE servers again.