in the galleries/grid_lightbox/css/common.css
change:
.pg-gl-tip {
width: 250px;
background-image: url(../images/dark_tip_top.png);
background-repeat: no-repeat;
background-position: 50% 0;
}
to:
.pg-gl-tip {
width: 250px;
background-image: url(../images/dark_tip_top.png);
background-repeat: no-repeat;
background-position: 50% 0;
display: none;
}