[remko]

Using debugger I watched the result and it is 0x00000005 so I inserted opcode ldc.i4.5.
Using reflector the code is now:

public static string Method_00(int num1)
{
    byte[] buffer;
    lock (typeof(Class_01))
    {
        if (Field_00 == null)
        {
            Assembly executingAssembly = Assembly.GetExecutingAssembly();
            Field_00 = executingAssembly.GetManifestResourceStream(executingAssembly.ManifestModule.ModuleVersionId.ToString("B"));
            byte[] publicKeyToken = executingAssembly.GetName().GetPublicKeyToken();
            if (publicKeyToken != null)
            {
                int num = 0;
                do
                {
                    Field_01 = 7;
                    num += 2;
                }
                while (num < (publicKeyToken.Length - 1));
            }
            Field_01 = 5;
        }

But still crashes