missing envelope icon on the topbar


I have Elgg 1.7.7 running on xampp. I modified the xampp's httpd-xampp.conf (allowing all) and on Elgg's side, I modified the site's url on site administration (set my ip address) to allow other people (like my boss) view from their pcs.

When viewed from other pcs, the PM icon (envelope icon) is missing though the link is still there. I am suspecting a problem on CSS file handling this.

Could anyone provide a lead on this issue? I would be very grateful.