Yes I encountered the same problem. I set out to fix it. Here is a fix to your problem

Go into \themes\default\templates and edit tpl_chat.php
Go to around line 874.
The block of code that starts with:
function write_message(INDATA){
if(yourData['ignore'][INDATA['uid']]) return;
and ends with:
INDATA['msg'] = INDATA['msg'].replace(/([A-z0-9_\-\.]+)@([A-z0-9\-\.]+)(?![^<>]*(>|<\/a>))/gi,"<a href=\"mailto: $1@$2\">$1@$2</a>");
Replace that entire code with this:
function write_message(INDATA){
if(yourData['ignore'][INDATA['uid']]) return;
INDATA['time'] = (yourData['settings']['show_timestamps']) ? '[' + gen_timestamp(INDATA['time']) + '] ' : '';
INDATA['msg'] = INDATA['msg'].replace(/</g,'<');
INDATA['msg'] = INDATA['msg'].replace(/>/g,'>');
INDATA['msg'] = INDATA['msg'].replace(/([^\/])www\./gi,'$1http://www.');
INDATA['msg'] = INDATA['msg'].replace(/\[url=(.+?)\](.+?)\[\/url\]/gi,"<a href='$1' target='_blank'>$2</a>");
INDATA['msg'] = INDATA['msg'].replace(/(http:\/\/|https:\/\/)([^ \[<]+)(?![^<>]*(>|<\/a>))/gi,"<a href=\"$1$2\" target=\"_blank\">$1$2</a>");
INDATA['msg'] = INDATA['msg'].replace(/<br \/>/g,"<br />");
INDATA['msg'] = INDATA['msg'].replace(/\\n/g,"<br />");
INDATA['msg'] = INDATA['msg'].replace(/([A-z0-9_\-\.]+)@([A-z0-9\-\.]+)(?![^<>]*(>|<\/a>))/gi,"<a href=\"mailto: $1@$2\">$1@$2</a>");
It's essentially changing '$' into an actual '$' sign.
I attached my copy of the file incase you mess up / don't understand what to do. (Don't forget to remove the .txt on the end of the file)
