Calendar not working

Hi Guys

We are experiencing a problem with our calendar plug in all of the sudden and I am not sure why.
We use to be able to click or hover the mouse over a date and it will bring up information, but now it is not working anymore.

Internet Explorer is reporting an error on the page:
Invalid argument.
Jquery.js line: 144
Code: 0 Char: 219

Can anyone help please?

Here is a copy of the error
Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1) ; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.04506.648; InfoPath.2; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
Timestamp: Thu, 14 Apr 2011 07:03:29 UTC

Message: Invalid argument.
Line: 144
Char: 219
Code: 0
URI: https://toyakankarate.com.au/blog/wp-includes/js/jquery/jquery.js?ver=1.4.2

Message: Invalid argument.
Line: 144
Char: 219
Code: 0
URI: https://toyakankarate.com.au/blog/wp-includes/js/jquery/jquery.js?ver=1.4.2

Message: Invalid argument.
Line: 144
Char: 219
Code: 0
URI: https://toyakankarate.com.au/blog/wp-includes/js/jquery/jquery.js?ver=1.4.2

Message: Invalid argument.
Line: 144
Char: 219
Code: 0
URI: https://toyakankarate.com.au/blog/wp-includes/js/jquery/jquery.js?ver=1.4.2

Message: Invalid argument.
Line: 144
Char: 219
Code: 0
URI: https://toyakankarate.com.au/blog/wp-includes/js/jquery/jquery.js?ver=1.4.2

Message: Invalid argument.
Line: 144
Char: 219
Code: 0
URI: https://toyakankarate.com.au/blog/wp-includes/js/jquery/jquery.js?ver=1.4.2

Message: Invalid argument.
Line: 144
Char: 219
Code: 0
URI: https://toyakankarate.com.au/blog/wp-includes/js/jquery/jquery.js?ver=1.4.2

Message: Invalid argument.
Line: 144
Char: 219
Code: 0
URI: https://toyakankarate.com.au/blog/wp-includes/js/jquery/jquery.js?ver=1.4.2

Message: Invalid argument.
Line: 144
Char: 219
Code: 0
URI: https://toyakankarate.com.au/blog/wp-includes/js/jquery/jquery.js?ver=1.4.2