我正在开发一个使用webservice我创建的 android 项目。几分钟前它工作正常，但突然开始出现以下错误。
源附件不包含文件 threadpoolexecutor.class 的源
Logcat 错误是：
07-10 11:30:22.844: E/AndroidRuntime(1707): FATAL EXCEPTION: AsyncTask #1
07-10 11:30:22.844: E/AndroidRuntime(1707): java.lang.RuntimeException: An error occured while executing doInBackground()
07-10 11:30:22.844: E/AndroidRuntime(1707): at android.os.AsyncTask$3.done(AsyncTask.java:299)
07-10 11:30:22.844: E/AndroidRuntime(1707): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
07-10 11:30:22.844: E/AndroidRuntime(1707): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
07-10 11:30:22.844: E/AndroidRuntime(1707): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
07-10 11:30:22.844: E/AndroidRuntime(1707): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
07-10 11:30:22.844: E/AndroidRuntime(1707): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
07-10 11:30:22.844: E/AndroidRuntime(1707): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
07-10 11:30:22.844: E/AndroidRuntime(1707): at java.lang.Thread.run(Thread.java:856)
07-10 11:30:22.844: E/AndroidRuntime(1707): Caused by: java.lang.NullPointerException
07-10 11:30:22.844: E/AndroidRuntime(1707): at com.example.backgroundTask.BackgroundTask.RegisterUser(BackgroundTask.java:125)
07-10 11:30:22.844: E/AndroidRuntime(1707): at com.example.backgroundTask.BackgroundTask.doInBackground(BackgroundTask.java:65)
07-10 11:30:22.844: E/AndroidRuntime(1707): at com.example.backgroundTask.BackgroundTask.doInBackground(BackgroundTask.java:1)
07-10 11:30:22.844: E/AndroidRuntime(1707): at android.os.AsyncTask$2.call(AsyncTask.java:287)
07-10 11:30:22.844: E/AndroidRuntime(1707): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
07-10 11:30:22.844: E/AndroidRuntime(1707): ... 4 more
07-10 11:30:23.174: W/Trace(1707): Unexpected value from nativeGetEnabledTags: 0
请告诉我可能导致此错误的原因，或者如果需要更多信息，请告诉我。
谢谢和问候..
Sourabh