If you're suddenly having problems with the display of custom-CSS userheads, just add !important before every semicolon in your userhead codes. Like so:

.ljuser img[src*="http://l-stat.livejournal.com/img/userinfo.gif"] {
width: 0px !important;
height: 0px !important;
padding: 13px 0px 0px 12px !important;
background: url(http://fatfrog.info/Ma/A/layout/meins/ljuser.png) no-repeat !important;
}

If that doesn't do the trick, check out the comments here.