diff --git a/mozilla/widget/src/os2/nsDirPicker.cpp b/mozilla/widget/src/os2/nsDirPicker.cpp
index 6e37d29cd3f..97dcf8e2134 100644
--- a/mozilla/widget/src/os2/nsDirPicker.cpp
+++ b/mozilla/widget/src/os2/nsDirPicker.cpp
@@ -134,6 +134,7 @@ struct DirPicker : public FS::ICallbacks
       // Create a new node
       PTREENODE pRec = (PTREENODE) WinSendMsg( hwndCnr, CM_ALLOCRECORD,
                                                MPFROMLONG(4), MPFROMLONG(1));
+      if( !pRec) return;
       // find some strings; note that fstree owns them
       pRec->m.pszIcon = (char*) aNewNode->GetFileInfo()->GetLeafName();
       if( aNewNode->AsDrive())
@@ -395,13 +396,6 @@ MRESULT EXPENTRY fndpDirPicker( HWND hwnd, ULONG msg, MPARAM mp1, MPARAM mp2)
         }
         break;
 
-      case WM_DESTROY:
-      {
-         pData->fsTree->DeleteInstance();
-         delete pData;
-         break;
-      }
-
       case WM_COMMAND:
          switch( SHORT1FROMMP(mp1))
          {
@@ -440,11 +434,11 @@ MRESULT EXPENTRY fndpDirPicker( HWND hwnd, ULONG msg, MPARAM mp1, MPARAM mp2)
                      }
                   }
                }
-
-               // break out, defdlgproc will close the window.
-               break;
+               // fall out, defdlgproc will close the window.
             }
          }
+         pData->fsTree->DeleteInstance();
+         delete pData;
          break;
 
       case WM_CLOSE:
diff --git a/mozilla/widget/src/os2/nsFSTree.cpp b/mozilla/widget/src/os2/nsFSTree.cpp
index aac4a844ca2..1b833fc95c7 100644
--- a/mozilla/widget/src/os2/nsFSTree.cpp
+++ b/mozilla/widget/src/os2/nsFSTree.cpp
@@ -399,7 +399,7 @@ BOOL fsTree::DeleteInstance()
 fsTree::~fsTree()
 {
    // Execute synchronously to prevent leaky pain
-   mDestructing = TRUE;   
+   mDestructing = TRUE;
    if( mRoot)
       DestroyNode( mRoot);
 
@@ -407,7 +407,11 @@ fsTree::~fsTree()
    mCBQueue.Close();
 
    if( mHEV)
+   {
+      if( mBuildMode != FS::Synchronous)
+         DosWaitEventSem( mHEV, SEM_INDEFINITE_WAIT); // Let async thread finish
       DosCloseEventSem( mHEV);
+   }
 
    if( mMutex)
       DosCloseMutexSem( mMutex);
@@ -515,6 +519,12 @@ void fsTree::Scan()
    // This lets the user thread go if we're synchronous.
    SendCompleteMsg();
 
+   if( mDestructing)
+   {
+      DosPostEventSem( mHEV);  // Just in case main thread is still waiting
+      return;
+   }
+
    // Process commands
    for(;;)
    {
@@ -589,6 +599,8 @@ void fsTree::CreateDrives()
    // go through the drives one by one
    for( UINT i = 0; i < ulDrives; i++)
    {
+      if( mDestructing) return;
+
       APIRET       rc;
       FILESTATUS3  fs3 = { { 0, 0, 0 } };
       FILEFINDBUF3 ffb3 = { 0 };
@@ -615,11 +627,13 @@ void fsTree::CreateDrives()
       SendMsg( pDrive, CBPacket::CreateNode);
    }
 
+
    // now scan for children.  Splitting the task up this way makes UIs more
    // responsive, as they can wap up the roots first before going digging.
    fsDir *pDir = mRoot->GetFirstChild();
    while( pDir)
    {
+      if( mDestructing) return;
       ScanForChildren( pDir);
       pDir = pDir->GetNextSibling();
    }
@@ -652,6 +666,8 @@ void fsTree::ScanForChildren( fsDir *aParent)
 
    while( !rc)
    {
+      if( mDestructing) break;
+
       if( strcmp( fb.achName, ".") && strcmp( fb.achName, ".."))
       {
          Lock();
@@ -755,6 +771,8 @@ void fsTree::Foliate( fsDir *aDir)
 
    while( !rc)
    {
+      if( mDestructing) break;
+
       Lock();
       fsFile *pFile = new fsFile( &fb, aDir);
       if( !pLast) aDir->SetFiles( pFile);
@@ -793,6 +811,8 @@ void fsTree::Notify()
          break;
       }
 
+      if( mDestructing) break;
+
       switch( pkt.mCmd)
       {
          case CBPacket::CreateRoot:
@@ -819,7 +839,7 @@ void fsTree::Notify()
 
          case CBPacket::ScanComplete:
             mCallbacks->InitialScanComplete();
-            if( mBuildMode == FS::Synchronous)
+//            if( mBuildMode == FS::Synchronous)
                DosPostEventSem( mHEV);
             break;
 
@@ -829,6 +849,8 @@ void fsTree::Notify()
       }
    }
 
+   DosPostEventSem( mHEV);  // Just in case the main thread is still waiting
+
    if( mNeedsPM)
    {
       WinDestroyMsgQueue( hmq);