title: Android billing exception
body: <p>I am testing my billing and I got this exception:</p>
  
  <pre><code>java.lang.IllegalStateException: Can't start async operation (launchPurchaseFlow) because another async operation(launchPurchaseFlow) is in progress.
          at utils.IabHelper.flagStartAsync(IabHelper.java:711)
          at utils.IabHelper.launchPurchaseFlow(IabHelper.java:316)
          at utils.IabHelper.launchPurchaseFlow(IabHelper.java:294)
          at com.problemio.SubscribeIntroActivity$6.onClick(SubscribeIntroActivity.java:117)
          at android.view.View.performClick(View.java:2532)
          at android.view.View$PerformClick.run(View.java:9308)
          at android.os.Handler.handleCallback(Handler.java:587)
          at android.os.Handler.dispatchMessage(Handler.java:92)
          at android.os.Looper.loop(Looper.java:150)
          at android.app.ActivityThread.main(ActivityThread.java:4293)
          at java.lang.reflect.Method.invokeNative(Native Method)
          at java.lang.reflect.Method.invoke(Method.java:507)
          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
          at dalvik.system.NativeStart.main(Native Method)
  </code></pre>
  
  <p>After I ran this code:</p>
  
  <pre><code>    Button subscribe = (Button)findViewById(R.id.subscribe);
      subscribe.setOnClickListener(new Button.OnClickListener() 
      {  
         public void onClick(View v) 
         {              
             // FIRST CHECK IF THE USER IS ALREADY A SUBSCRIBER.
            mHelper.launchPurchaseFlow(SubscribeIntroActivity.this, SUBSCRIBE_SKU, RC_REQUEST, mPurchaseFinishedListener);
  
         }
      });   
  </code></pre>
  
  <p>But prior to this I ran it as a test user and with the test product id which was this: android.test.purchased and it worked. But when I changed product id to one of my own products ids, it crashed with the exception above.</p>
  
  <p>Any ideas why that happened?
  Thanks!</p>