I was testing your on-line demo http://www.phpfreechat.net/demo.en.php with both Firefox (1.5) and Internet Explorer (6.0.2900.2180.xpsp2_gdr.050301-1519) and with IE I've found a little bug in javascript:
if you cut down the chat and press F5 (or update page) you have an [object Error] message!
That's all!