diff -r cc75c76972ee -r c0432d11811c src/multimedia/audio/qaudioinput_win32_p.cpp
--- a/src/multimedia/audio/qaudioinput_win32_p.cpp	Wed Apr 21 12:15:23 2010 +0300
+++ b/src/multimedia/audio/qaudioinput_win32_p.cpp	Wed Apr 21 20:15:53 2010 +0300
@@ -57,8 +57,6 @@
 
 //#define DEBUG_AUDIO 1
 
-static CRITICAL_SECTION waveInCriticalSection;
-
 static const int minimumIntervalTime = 50;
 
 QAudioInputPrivate::QAudioInputPrivate(const QByteArray &device, const QAudioFormat& audioFormat):
@@ -104,16 +102,16 @@
         case WIM_OPEN:
             break;
         case WIM_DATA:
-            EnterCriticalSection(&waveInCriticalSection);
+            EnterCriticalSection(&qAudio->waveInCriticalSection);
             if(qAudio->waveFreeBlockCount > 0)
                 qAudio->waveFreeBlockCount--;
             qAudio->feedback();
-            LeaveCriticalSection(&waveInCriticalSection);
+            LeaveCriticalSection(&qAudio->waveInCriticalSection);
             break;
         case WIM_CLOSE:
-            EnterCriticalSection(&waveInCriticalSection);
+            EnterCriticalSection(&qAudio->waveInCriticalSection);
             qAudio->finished = true;
-            LeaveCriticalSection(&waveInCriticalSection);
+            LeaveCriticalSection(&qAudio->waveInCriticalSection);
             break;
         default:
             return;
@@ -158,7 +156,8 @@
     int count = buffer_size/period_size;
 
     for(int i = 0; i < count; i++) {
-        waveInUnprepareHeader(hWaveIn,&blocks[i], sizeof(WAVEHDR));
+        if (blocks->dwFlags & WHDR_PREPARED)
+            waveInUnprepareHeader(hWaveIn,blocks, sizeof(WAVEHDR));
         blocks+=sizeof(WAVEHDR);
     }
     HeapFree(GetProcessHeap(), 0, blockArray);
@@ -226,8 +225,8 @@
 #endif
     header = 0;
     if(buffer_size == 0) {
-        // Default buffer size, 100ms, default period size is 20ms
-        buffer_size = settings.frequency()*settings.channels()*(settings.sampleSize()/8)*0.1;
+        // Default buffer size, 200ms, default period size is 40ms
+        buffer_size = settings.frequency()*settings.channels()*(settings.sampleSize()/8)*0.2;
 	period_size = buffer_size/5;
     } else {
         period_size = buffer_size/5;