diff -Naur qt-orig/src/gui/kernel/qapplication_x11.cpp qt/src/gui/kernel/qapplication_x11.cpp
--- qt-orig/src/gui/kernel/qapplication_x11.cpp	2010-04-05 07:46:27 +0400
+++ qt/src/gui/kernel/qapplication_x11.cpp	2010-05-10 10:39:39 +0400
@@ -4280,6 +4280,10 @@
             }
 #endif
             type = QEvent::MouseButtonRelease;
+	    // HACK: if recieved ButtonRelease event qt_button_down - can't be NULL, because
+	    // no ButtonRelease without ButtonPress event
+            if (!qt_button_down)
+                qt_button_down = this;
         }
     }
     mouseActWindow = effectiveWinId();                        // save some event params