Check in the console of each browser. In safari you may have to enable the developer menu (under the advanced settings pane if I remember correctly), not sure about chrome, IE sucks at debugging, so don't bother there, and in firefox, install the
firebug addonSee if that gives you any errors, as it may be that something in the javascript has died and the operator is no longer being connected, despite what it may tell you.
Your other option is to try reinstalling HCL (you can keep your database settings most likely, just back them up first) as that may fix a bugged file.
Or, if this is hosted somewhere, look for the debug file on the forums and post a link to it and someone (probably me, seeing as the administrators are busy) can take a look at it (and admin access might help too

). Just PM any confidential information (like admin accounts if you decide to go that route).