I read many posts here and on other sites, but can not find the problem creating my Error: I use an AsyncTask because I want to easily manipulate the UI Thread before and after Execution. In doInBackground I create a ThreadPoolExecutor and execute Runnables. If I only execute 1 Runnable with the Executor, there is no Problem, but if I execute another Runnable I get following Error: 06-26 18:00:42.288: A/libc(25073): Fatal signal 11 (SIGSEGV) at 0x7f486162 (code=1), thread 25106 (pool-1-thread-2) 06-26 18:00:42.304: D/dalvikvm(25073): GC_CONCURRENT freed 119K, 2% free 8908K/9056K, paused 4ms+4ms, total 45ms 06-26 18:00:42.327: I/System.out(25073): In Check All with Prefix: a and Length: 4 06-26 18:00:42.390: I/DEBUG(126): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** 06-26 18:00:42.390: I/DEBUG(126): Build fingerprint: 'google/yakju/maguro:4.2.2/JDQ39/573038:user/release-keys' 06-26 18:00:42.390: I/DEBUG(126): Revision: '9' 06-26 18:00:42.390: I/DEBUG(126): pid: 25073, tid: 25106, name: pool-1-thread-2 >>> de.uni_duesseldorf.cn.distributed_computing2 <<< 06-26 18:00:42.390: I/DEBUG(126): signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 7f486162 ... 06-26 18:00:42.538: I/DEBUG(126): memory map around fault addr 7f486162: 06-26 18:00:42.538: I/DEBUG(126): 60292000-60391000 06-26 18:00:42.538: I/DEBUG(126): (no map for address) 06-26 18:00:42.538: I/DEBUG(126): bed14000-bed35000 [stack] I set up the ThreadPoolExecutor like this: // numberOfPackages: Number of Runnables to be executed public void initializeThreadPoolExecutor (int numberOfPackages) { int corePoolSize = Runtime.getRuntime().availableProcessors(); int maxPoolSize = numberOfPackages; long keepAliveTime = 60; final BlockingQueue workingQueue = new LinkedBlockingQueue(); executor = new ThreadPoolExecutor(corePoolSize, maxPoolSize, keepAliveTime, TimeUnit.SECONDS, workingQueue); } I have no clue, why it fails when starting the second Thread. Maybe Memory Leaks? Any Help appreciated. Thanks in Advance