Happening on windows and unix, probably mac as well. With this stack trace: #0 0x1 in ?? () #1 0x419fb61d in nsGenericElement::HandleDOMEvent (this=0x82ff5dc, aPresContext=@0x813a7d8, aEvent=0xbfffe2ac, aDOMEvent=0xbfffe250, aFlags=1, aEventStatus=@0xbfffe2e4) at nsGenericElement.cpp:779 #2 0x418bf80d in nsHTMLSelectElement::HandleDOMEvent (this=0x82ff5b8, aPresContext=@0x813a7d8, aEvent=0xbfffe2ac, aDOMEvent=0x0, aFlags=1, aEventStatus=@0xbfffe2e4) at nsHTMLSelectElement.cpp:801 #3 0x41807a48 in nsEventStateManager::GenerateMouseEnterExit (this=0x82d9830, aPresContext=@0x813a7d8, aEvent=0xbfffe70c) at nsEventStateManager.cpp:621 #4 0x41806495 in nsEventStateManager::PreHandleEvent (this=0x82d9830, aPresContext=@0x813a7d8, aEvent=0xbfffe70c, aTargetFrame=0x8169bb8, aStatus=@0xbfffe67c, aView=0x82dab78) at nsEventStateManager.cpp:127 #5 0x41847f8e in PresShell::HandleEvent (this=0x825b468, aView=0x82dab78, aEvent=0xbfffe70c, aEventStatus=@0xbfffe67c) at nsPresShell.cpp:1866 #6 0x41b94b43 in nsView::HandleEvent (this=0x82dab78, event=0xbfffe70c, aEventFlags=8, aStatus=@0xbfffe67c, aHandled=@0xbfffe620) at nsView.cpp:834 #7 0x41b94ad2 in nsView::HandleEvent (this=0x82fad00, event=0xbfffe70c, aEventFlags=8, aStatus=@0xbfffe67c, aHandled=@0xbfffe620) at nsView.cpp:818 #8 0x41b94ad2 in nsView::HandleEvent (this=0x82fac50, event=0xbfffe70c, aEventFlags=8, aStatus=@0xbfffe67c, aHandled=@0xbfffe620) at nsView.cpp:818 #9 0x41b94ad2 in nsView::HandleEvent (this=0x8260870, event=0xbfffe70c, aEventFlags=28, aStatus=@0xbfffe67c, aHandled=@0xbfffe620) at nsView.cpp:818 #10 0x41b9de53 in nsViewManager::DispatchEvent (this=0x8260690, aEvent=0xbfffe70c, aStatus=@0xbfffe67c) at nsViewManager.cpp:1609 #11 0x41b92c64 in HandleEvent (aEvent=0xbfffe70c) at nsView.cpp:66 #12 0x405b9462 in nsWidget::DispatchEvent (this=0x82d6870, event=0xbfffe70c, aStatus=@0xbfffe6b8) at nsWidget.cpp:1199 #13 0x405b918c in nsWidget::DispatchWindowEvent (this=0x82d6870, event=0xbfffe70c) at nsWidget.cpp:1065 #14 0x405b9520 in nsWidget::DispatchMouseEvent (this=0x82d6870, aEvent=@0xbfffe70c) at nsWidget.cpp:1226 #15 0x405b9ce0 in nsWidget::OnMotionNotifySignal (this=0x82d6870, aGdkMotionEvent=0x8137ba8) at nsWidget.cpp:1495 #16 0x405ba88e in nsWidget::MotionNotifySignal (aWidget=0x81cdda8, aGdkMotionEvent=0x8137ba8, aData=0x82d6870) at nsWidget.cpp:2016

Fixed.

verified fixed on 1999-09-13-08-M10 RedHat Linux 6.0 (GNOME/enlightenment) 1999-09-13-08-M10 WinNT 4.0 sp5 1999-09-13-08-M10 MacOS 8.51