try win32-process gem

lib/middleman.rb

@@ -171,6 +171,8 @@ module Middleman
     app.set :environment, options[:environment].to_sym
     opts[:app] = app.new
     opts[:server] = 'thin'
+
+    $stderr.puts "== The Middleman is standing watch on port #{opts[:Port]}"
     ::Rack::Server.new(opts).start
   end
 end

lib/middleman/guard.rb

@@ -59,8 +59,6 @@ module Guard
       @server_job = fork do
         ::Middleman.start_server(@options)
       end
-
-      puts "== The Middleman is standing watch on port #{@options[:port]}"
     end
   
     def server_stop
@@ -68,7 +66,7 @@ module Guard
       Process.kill("KILL", @server_job)
       Process.wait @server_job
       @server_job = nil
-      @server_options[:app] = nil
+      # @server_options[:app] = nil
     end
   end
 end