1. open the context menu on a taskbar button for a window that is not focused 2. expand the "send to" submenu 3. wait for an urgency hint on the window that belongs to that selected taskbar button. once the urgency hint occurs, all X input is blocked. programs still run, for example new messages in xchat arrive, but you can't select or write anything or run any applications like xfrun4 or xkill. the only solution is to log in on a tty or via ssh etc and kill xfce4-panel. once it has been killed, you can restart it and everything will continue as usual. reproducable: always it will not work, if you open the context menu on a button for a window that does not receive the urgency hint and it will not work either, when you don't expand the "send to" submenu.
Aha, good catch. I'll have a look, but I think it might be tricky to avoid this.
Could you give a status update on this bug using the trunk libwmck tasklist?
No response in a while and because we use wnck for the menu, this is not an issue in the panel.