Mootools and jqeury conflicts/errors - jLive Live Chat debugging

When our Joomla 3 site loads, the following error is thrown by mootools-core.js:

'Uncaught TypeError: Cannot read property 'parentNode' of null '

We don't know what's causing the error, whether it's the Beez template or one of our many plugins and modules. We're eliminating js errors on the page in an effort to debug our jLive Live Chat add on, which isn't working as expected in Chrome/OS. All other browsers in OS/Windows are fine.

When using jLive live chat with Chrome/OS, we get the following errors when we begin a chat, which never starts. Instead, 'please wait...connecting' is displayed endlessly.

1. 'event.returnValue is deprecated. Please use the standard event.preventDefault() instead. '

2. 'POST http://ourwebsite/index.php?option=com_jlivechat&view=popup&tmpl=component 500 (Internal Server Error) jquery-1.7.2.min.js:4

send jquery-1.7.2.min.js:4

f.extend.ajax jquery-1.7.2.min.js:4

JLiveChat.monitorPendingChatSession jlivechat.min.js:1

(anonymous function)'

jLive Chat says we should disable Zenguard, which we haven't yet done, as inmotion support did not feel it necessary. We have however added several outdated jquery libraries (1.7, 1.6), at the suggestion of jLive's support. The library additions do not correct the Chrome/OS issue with jLive live chat.

Strangely, when we close the chat window, with it's spinning 'please wait' message, and reopen, the chat has started, and we can communicate with the operator.

Any suggestions for fixes are much appreciated!