I have whisker menu plugin installed (1.4.x/1.5.0) and whenever one drags elements around within the panel "window buttons" applet the whisker menu icon disappears and becomes black. I have been reported this to the whisker developer and he said that this might be a problem within xfce4-panel. It would be nice to have this one fixed (if possible) before 4.12 release. Thanks.
Duplicate of 10656. *** This bug has been marked as a duplicate of bug 10656 ***