It's strange a bit but your 'Help' menu seems to be nested in 'Authorization' according to layout.
You have to change layout or use
Code:
.menu-auth .menu-help .title-bar img.icon { background: url(images/dingbats_help.gif) no-repeat; }
instead of
Code:
#left-bar .menu-help .title-bar img.icon { background: url(images/dingbats_help.gif) no-repeat; }