I had have thesame problem with, IE (Windows), Firefox (MacOs, Windows), Opera (Linux, MacOs), Safari 2 (MacOs).
Server Apache version 1.3.37 (Unix), PHP version 4.4.4, MySQL version 4.1.22-standard, HCL 2.1.2.
I had cheked de permisions and the icons files are chmodded 644, the icons folder is chmodded 777.
In the errors logs no there are 404 errors on image (png, gif, or jpg).
I uploaded custom icons and doesn't work.
I use the help center with this code
')" target="_blank"><img src="http://www.luciaw-adv.com.ar/hcl/icons/online.gif
" alt="Haga clic aqu? para Consultas On-line" /></a>
and load icons and work the chat but doesn't work cobrowser, doesn't update the icon (on-line - off-line).....
This site was run in other server ok when moved to new server dosen't work.
I installed help center again but I had have the same problem.