End User Is Only Seeing HTML

I have a client who is using FCKEditor to modify the contents of his site. However, lately every time that he tries to edit his site, he is not given a WYSIWYG editor at all. All that he sees is HTML. Oddly enough this happens both in IE and FF. It also happens with an alternative editor (http://www.siteobjects.com). Many other users are using the same code, and they are not having any problems. He says that the only thing that he has installed during this time is AVG Antivirus. I run AVG myself and have not seen this problem. Have any of you guys ran into it? This client is not local, so if you have any questions that will help me diagnose the problem, I would appreciate it. He is running Windows XP and IE v. 7.0.5730.11 and the latest version of FF. Any help would be great. Thanks!