diff --git a/harbour/ChangeLog b/harbour/ChangeLog
index fef5f0195e..2af78a9479 100644
--- a/harbour/ChangeLog
+++ b/harbour/ChangeLog
@@ -8,6 +8,17 @@
    2008-12-31 13:59 UTC+0100 Foo Bar (foo.bar foobar.org)
 */
 
+2008-10-30 15:03 UTC+0100 Przemyslaw Czerpak (druzus/at/priv.onet.pl)
+  * harbour/include/hbvmpub.h
+    + added HB_VM_ISFUNC(), HB_VM_FUNCUNREF() and HB_VM_EXECUTE()
+      macros to operate on HB_SYMB structure
+
+  * harbour/source/vm/hvm.c
+  * harbour/source/vm/classes.c
+     * use HB_VM_ISFUNC()/HB_VM_FUNCUNREF()/HB_VM_EXECUTE() macros
+       for executing function inside HB_SYMB structure to avoid possible
+       synchronization problems during modifications
+
 2008-10-29 19:06 UTC-0800 Pritpal Bedi (pritpal@vouchcac.com)
   * harbour/contrib/gtwvg/gtwvg.c
   * harbour/contrib/gtwvg/gtwvg.h
diff --git a/harbour/include/hbvmpub.h b/harbour/include/hbvmpub.h
index 2c926b7b81..89454ec804 100644
--- a/harbour/include/hbvmpub.h
+++ b/harbour/include/hbvmpub.h
@@ -92,6 +92,25 @@ struct _HB_SYMB;
                   } \
                } while( 0 )
 
+#define HB_VM_ISFUNC( pSym ) ( ( pSym )->value.pFunPtr )
+
+#define HB_VM_FUNCUNREF( pSym ) \
+               do { \
+                  if( ( ( pSym )->scope.value & HB_FS_DEFERRED ) && \
+                      ( pSym )->pDynSym ) \
+                     pSym = ( pSym )->pDynSym->pSymbol; \
+               } while( 0 )
+
+#define HB_VM_EXECUTE( pSym ) \
+               do { \
+                  /* Running pCode dynamic function from .hrb? */ \
+                  if( ( pSym )->scope.value & HB_FS_PCODEFUNC ) \
+                     hb_vmExecute( ( pSym )->value.pCodeFunc->pCode, \
+                                   ( pSym )->value.pCodeFunc->pSymbols ); \
+                  else \
+                     ( pSym )->value.pFunPtr(); \
+               } while( 0 )
+
    /* dynamic symbol structure */
    typedef struct _HB_DYNS
    {
diff --git a/harbour/source/vm/classes.c b/harbour/source/vm/classes.c
index b3a4ecd54e..1210bea0b3 100644
--- a/harbour/source/vm/classes.c
+++ b/harbour/source/vm/classes.c
@@ -4133,14 +4133,11 @@ static HARBOUR hb___msgDelegate( void )
    PMETHOD pMethod = pClass->pMethods + pStack->uiMethod;
    PHB_SYMB pExecSym = pClass->pMethods[ pMethod->uiData ].pFuncSym;
 
-   if( pExecSym && pExecSym->value.pFunPtr )
+   if( pExecSym )
+      HB_VM_FUNCUNREF( pExecSym );
+   if( pExecSym && HB_VM_ISFUNC( pExecSym ) )
    {
-      if( pExecSym->scope.value & HB_FS_PCODEFUNC )
-         /* Running pCode dynamic function from .hrb */
-         hb_vmExecute( pExecSym->value.pCodeFunc->pCode,
-                       pExecSym->value.pCodeFunc->pSymbols );
-      else
-         pExecSym->value.pFunPtr();
+      HB_VM_EXECUTE( pExecSym );
    }
    else
    {
@@ -4155,7 +4152,9 @@ static HARBOUR hb___msgSync( void )
    PMETHOD pMethod = pClass->pMethods + pStack->uiMethod;
    PHB_SYMB pExecSym = pMethod->pRealSym;
 
-   if( pExecSym && pExecSym->value.pFunPtr )
+   if( pExecSym )
+      HB_VM_FUNCUNREF( pExecSym );
+   if( pExecSym && HB_VM_ISFUNC( pExecSym ) )
    {
       PHB_ITEM pObject = hb_stackSelfItem();
       USHORT uiClass = hb_objGetClass( pObject );
@@ -4166,13 +4165,7 @@ static HARBOUR hb___msgSync( void )
 
       if( !pMutex || hb_threadMutexLock( pMutex ) )
       {
-         if( pExecSym->scope.value & HB_FS_PCODEFUNC )
-            /* Running pCode dynamic function from .hrb */
-            hb_vmExecute( pExecSym->value.pCodeFunc->pCode,
-                          pExecSym->value.pCodeFunc->pSymbols );
-         else
-            pExecSym->value.pFunPtr();
-
+         HB_VM_EXECUTE( pExecSym );
          if( pMutex )
             hb_threadMutexUnlock( pMutex );
       }
@@ -4190,18 +4183,15 @@ static HARBOUR hb___msgSyncClass( void )
    PMETHOD pMethod = pClass->pMethods + pStack->uiMethod;
    PHB_SYMB pExecSym = pMethod->pRealSym;
 
-   if( pExecSym && pExecSym->value.pFunPtr )
+   if( pExecSym )
+      HB_VM_FUNCUNREF( pExecSym );
+   if( pExecSym && HB_VM_ISFUNC( pExecSym ) )
    {
-      if( hb_threadMutexLock( pClass->pMutex ) )
+      if( !pClass->pMutex || hb_threadMutexLock( pClass->pMutex ) )
       {
-         if( pExecSym->scope.value & HB_FS_PCODEFUNC )
-            /* Running pCode dynamic function from .hrb */
-            hb_vmExecute( pExecSym->value.pCodeFunc->pCode,
-                          pExecSym->value.pCodeFunc->pSymbols );
-         else
-            pExecSym->value.pFunPtr();
-
-         hb_threadMutexUnlock( pClass->pMutex );
+         HB_VM_EXECUTE( pExecSym );
+         if( pClass->pMutex )
+            hb_threadMutexUnlock( pClass->pMutex );
       }
    }
    else
diff --git a/harbour/source/vm/hvm.c b/harbour/source/vm/hvm.c
index 66bfcee4f8..49f12f5ebf 100644
--- a/harbour/source/vm/hvm.c
+++ b/harbour/source/vm/hvm.c
@@ -5363,17 +5363,13 @@ HB_EXPORT void hb_vmDo( USHORT uiParams )
       PHB_SYMB pExecSym;
 
       pExecSym = hb_objGetMethod( pSelf, pSym, &sStackState );
-      if( pExecSym && ( pExecSym->scope.value & HB_FS_DEFERRED ) && pExecSym->pDynSym )
-         pExecSym = pExecSym->pDynSym->pSymbol;
-      if( pExecSym && pExecSym->value.pFunPtr )
+      if( pExecSym )
+         HB_VM_FUNCUNREF( pExecSym );
+      if( pExecSym && HB_VM_ISFUNC( pExecSym ) )
       {
          HB_TRACE_PRG(("Calling: %s:%s", hb_objGetClsName( pSelf ), pSym->szName));
-         if( pExecSym->scope.value & HB_FS_PCODEFUNC )
-            /* Running pCode dynamic function from .hrb */
-            hb_vmExecute( pExecSym->value.pCodeFunc->pCode,
-                          pExecSym->value.pCodeFunc->pSymbols );
-         else
-            pExecSym->value.pFunPtr();
+
+         HB_VM_EXECUTE( pExecSym );
 
 #ifndef HB_NO_PROFILER
          if( bProfiler )
@@ -5387,21 +5383,17 @@ HB_EXPORT void hb_vmDo( USHORT uiParams )
    }
    else /* it is a function */
    {
-      if( ( pSym->scope.value & HB_FS_DEFERRED ) && pSym->pDynSym )
-         pSym = pSym->pDynSym->pSymbol;
-      if( pSym->value.pFunPtr )
+      HB_VM_FUNCUNREF( pSym );
+      if( HB_VM_ISFUNC( pSym ) )
       {
          HB_TRACE_PRG(("Calling: %s", pSym->szName));
+
 #ifndef HB_NO_PROFILER
          if( bProfiler && pSym->pDynSym )
             pSym->pDynSym->ulRecurse++;
 #endif
-         /* Running pCode dynamic function from .hrb? */
-         if( pSym->scope.value & HB_FS_PCODEFUNC )
-            hb_vmExecute( pSym->value.pCodeFunc->pCode,
-                          pSym->value.pCodeFunc->pSymbols );
-         else
-            pSym->value.pFunPtr();
+
+         HB_VM_EXECUTE( pSym );
 
 #ifndef HB_NO_PROFILER
          if( bProfiler && pSym->pDynSym )
@@ -5454,18 +5446,13 @@ HB_EXPORT void hb_vmSend( USHORT uiParams )
    pSelf = hb_stackSelfItem();   /* NIL, OBJECT or BLOCK */
 
    pExecSym = hb_objGetMethod( pSelf, pSym, &sStackState );
-   if( pExecSym && ( pExecSym->scope.value & HB_FS_DEFERRED ) && pExecSym->pDynSym )
-      pExecSym = pExecSym->pDynSym->pSymbol;
-   if( pExecSym && pExecSym->value.pFunPtr )
+   if( pExecSym )
+      HB_VM_FUNCUNREF( pExecSym );
+   if( pExecSym && HB_VM_ISFUNC( pExecSym ) )
    {
       HB_TRACE_PRG(("Calling: %s:%s", hb_objGetClsName( pSelf ), pSym->szName));
 
-      if( pExecSym->scope.value & HB_FS_PCODEFUNC )
-         /* Running pCode dynamic function from .hrb */
-         hb_vmExecute( pExecSym->value.pCodeFunc->pCode,
-                    pExecSym->value.pCodeFunc->pSymbols );
-      else
-         pExecSym->value.pFunPtr();
+      HB_VM_EXECUTE( pExecSym );
 
 #ifndef HB_NO_PROFILER
       if( bProfiler )