Hello,
the error states that you are missing a file 'log4net.dll'. The Steam's verification of a game cache should restore it automatically.

• Could you please check whether this file exists on your hard drive: "C:\Steam\steamapps\common\Arma 3\Launcher\log4net.dll".
• You've stated that you have already run the verification of the game cache. What was the result of the verification? Was everything alright or did Steam re-downloaded some files.
• Do you have some antivirus product installed?

File is where it's supposed to be; verification says "all files successfully validated". Also tried deleting and validating, it re-downloaded but I'm still getting the error

I'm running avg

Ok, that is pretty serious problem then.

I've create a small application allows you to enable a diagnostics of how the Launcher DLLs are loaded: http://arma.jiripolasek.com/files/AssemblyBindingLog.zip

I'd like to ask you to run the application, enable the logging, run Launcher and then compress and upload the logs (and then disable the logging).

There may be a yet another explanation with a simple solution. Windows has a security feature that prevents files downloaded from the internet from being run.

1. Right-click on log4net.dll then click on Properties;
2. Go to a General tab;
3. Click on a Unblock button.

There's no unblock button in the general tab of the properties.

Also I tried running the program (as administrator and from the arma3 and launcher folder) but it didn't return any logs after trying to launch

Have you installed all net.framworks available for your system?

Was a folder "Fusion Logs" created on your desktop? Is it empty?

Nvm, managed to manually enable logs from registry editor, here they are.

https://dl.dropboxusercontent.com/u/19380428/Fusion%20Logs.rar

Hello,
for some unknown reason you have an old file in a wrong directory and it cause the conflict. Remove the "C:\Steam\steamapps\common\Arma 3\SharedResources.dll" file and try it to run Launcher again. (The correct file should be located in Launcher subfolder with version 1.2.xxx).

Did that, got a new error:

System.MissingMethodException: Method not found: 'Void Utils.ApplicationExtension.RestartAndExit(System.Windows.Application, System.String, Int32)'.

at Launcher.App.OnStartup(StartupEventArgs e)
at System.Windows.Application.<.ctor>b__1(Object unused)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
at System.Windows.Threading.DispatcherOperation.InvokeImpl()
at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Windows.Threading.DispatcherOperation.Invoke()
at System.Windows.Threading.Dispatcher.ProcessQueue()
at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
at System.Windows.Threading.Dispatcher.Run()
at System.Windows.Application.RunDispatcher(Object ignore)
at System.Windows.Application.RunInternal(Window window)
at System.Windows.Application.Run(Window window)
at Launcher.StartUp.StartGui(InitArgs param)
at Launcher.StartUp.HandleCommandLine()

I'd guess that this can be fixed by deleting of a file "C:\Steam\steamapps\common\Arma 3\Utils.dll".

If you also have any of these files directly in Arma 3 folder, delete them too:

• protobuf-net.dll,
• SteamLayer.dll,
• SteamLayerWrap.dll,
• Xceed.Wpf.Toolkit.dll

Deleted them all (except steamlayerwrap, didn't have that one) and it's still not launching but it doesn't create txt files on the desktop anymore

If you have any of these folders in Arma 3 folder, please, delete them too:

• cs-cz;
• de-de;
• en-us;
• es-es;
• fr-fr;
• it-it;
• pl-pl;
• pt-br;
• ru-ru

Oh that did the trick =) thank you very much!

Splendidly done. Thank you for your cooperation.