Version:            (using KDE KDE 3.1.93)
Installed from:    Gentoo Packages
Compiler:          gcc 3.2.3 
OS:          Linux

When closing ytalk 3.1.1 (a talk-application from http://www.iagora.com/~espel/ytalk/ytalk.html ), kwin crashes (so all the windows lose their title bar, I can restart it from console). It does so every time, but only with the Web Window Decoration.  

With web window decoration, from the backtrace:
(no debugging symbols found)...(no debugging symbols found)...
(no debugging symbols found)...(no debugging symbols found)...
(no debugging symbols found)...(no debugging symbols found)...
(no debugging symbols found)...(no debugging symbols found)...
(no debugging symbols found)...(no debugging symbols found)...
(no debugging symbols found)...[New Thread 16384 (LWP 8746)]
0x40dc7137 in waitpid ()
   from /lib/libpthread.so.0
#0  0x40dc7137 in waitpid () from /lib/libpthread.so.0
#1  0x4044549d in KCrash::defaultCrashHandler(int) ()
   from /usr/kde/3.2/lib/libkdecore.so.4
#2  0x40dc5fea in __pthread_sighandler () from /lib/libpthread.so.0
#3  <signal handler called>
#4  0x00200069 in ?? ()
#5  0x4054ae59 in Web::WebButton::mouseReleaseEvent(QMouseEvent*) ()
   from /usr/kde/3.2/lib/kde3/kwin3_web.so
#6  0x4085532c in QWidget::event(QEvent*) () from /usr/qt/3/lib/libqt-mt.so.3
#7  0x407c5e35 in QApplication::internalNotify(QObject*, QEvent*) ()
   from /usr/qt/3/lib/libqt-mt.so.3
#8  0x407c5318 in QApplication::notify(QObject*, QEvent*) ()
   from /usr/qt/3/lib/libqt-mt.so.3
#9  0x403b180e in KApplication::notify(QObject*, QEvent*) ()
   from /usr/kde/3.2/lib/libkdecore.so.4
#10 0x4075eff8 in QETWidget::translateMouseEvent(_XEvent const*) ()
   from /usr/qt/3/lib/libqt-mt.so.3
#11 0x4075c699 in QApplication::x11ProcessEvent(_XEvent*) ()
   from /usr/qt/3/lib/libqt-mt.so.3
#12 0x407735e7 in QEventLoop::processEvents(unsigned) ()
   from /usr/qt/3/lib/libqt-mt.so.3
#13 0x407d8ff6 in QEventLoop::enterLoop() () from /usr/qt/3/lib/libqt-mt.so.3
#14 0x407d8e98 in QEventLoop::exec() () from /usr/qt/3/lib/libqt-mt.so.3
#15 0x407c6081 in QApplication::exec() () from /usr/qt/3/lib/libqt-mt.so.3
#16 0x4004e4ee in kdemain () from /usr/kde/3.2/lib/libkdeinit_kwin.so
#17 0x080485eb in kdemain ()
#18 0x40f057a7 in __libc_start_main () from /lib/libc.so.6

Console output:
$ ytalk iam504@kronos
X connection to :0.0 broken (explicit kill or server shutdown).

(The talk session was not established.)

However, with the Keramik KWin does not crash. Instead the window disappears, but does not return the console prompt. After a CRTL-C the same X connection error message apears on console. I tried switching back to Web and closing ytalk crashed KWin again.