This problem also happens with Mootools 1.2.4 plugin.
When Mootools upgrade plugin is enabled, tool tip does not display when hover over and there is javascript error.

Firebug shows:
this.container is undefined

and IE:
Message: 'this.container' is null or not an object
Line: 3
Char: 103099
Code: 0
URI: www.victoriatw.com/components/com_gantry/js/mootools-1.2.5.js

Anyone else has the same problem? Is it because this calendar module uses older version of Mootools?
Any advice is appreciated!

Hi TheSin,

Can you please show me where/how to update mootools script the calendar uses to the one native to Joomla?

Yes - the calendar uses the old Mootools

Regards
Toni

if you check the JS from my 1.6 attempt I had to update all the code to mootools form 1.6 which is 1.3 IIRC, likely more compat with 1.2.5 though.