Labels on some buttons in Xchat windows don't display correctly. It's not possible to use Alt+Letter key sequence to perform action on a button. I've include sample screenshot. I've found, that buttons which created with gtk_button_new_with_mnemonic gtk function don't have such problem, but those which are created with gtk_button_new (http://library.gnome.org/devel/gtk/unstable/GtkButton.html#gtk-button-new). The fix would to alter function gtkutil_button in file fe-gtk/gtkutil.c, line 368 (svn, r1459) to call gtk_button_new_with_mnemonic.