Its probably because you removed JUST THE IMAGE code and not the actual link.
vbulletin tries to play nice with seo so now basically your forum is trying to load either "Leo's" Avatar or "Online.gif" image and since it cant it says "Leo" or "Online" twice.. as your pretty much stating..
Hope that makes sense.. er, lemme give you a code reference.. (hope im not being stupid here, been awake like 30 hours..)
Code:
<a href="#" title="leo"><img src="leo.gif" alt="Online"></img></a>
so basicly you removed "leo.gif" but now "Online" is showing, vise versa.. I think ..
p.s. did i mention im tired ? -,- really tired