"Binary Radio Pulsar Search (Arecibo, GPU) 1.39 (BRP4G-opencl-ati)" application won't quit

I closed the BOINC Manager and I have set it to stop all tasks while exiting. But I noticed that the application "Binary Radio Pulsar Search (Arecibo, GPU) 1.39 (BRP4G-opencl-ati)" had not stopped. So I again started BOINC Manager and now none of the tasks start saying, "Suspended, CPU in use" (more than 25% use of CPU by the above mentioned app). So I just killed the application and now other tasks started but not this one saying "waiting for lock".