Make sure Plutonium isn't running.
Plutonium.Updater.Core.Models.UpdateException: Failed to update file bin/plutonium-launcher-win32.exe ---> System.IO.IOException: The process cannot access the file 'C:\Users\mikey\AppData\Local\Plutonium\bin\plutonium-launcher-win32.exe' because it is being used by another process.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
at System.IO.File.InternalWriteAllBytes(String path, Byte[] bytes, Boolean checkHost)
at Plutonium.Updater.Core.Updater.<Run>d__23.MoveNext()
--- End of inner exception stack trace ---
at Plutonium.Updater.Core.Updater.<Run>d__23.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Plutonium.Updater.App.Windows.UpdateWindow.<UpdateWindow_Loaded>d__6.MoveNext()