Need some more detail to understand what's your problem. Don't you have a public URL where to test your code?

i think it should mean BODY, search your code and you will find it ;)

Hi, I've got "almost" the same error, I received these 2 erros with IE 8.0:

Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET4.0C; .NET4.0E; InfoPath.1)

Timestamp: Thu, 24 Feb 2011 16:14:55 UTC

Message: 'document.body' is null or not an object
Line: 8148
Char: 4
Code: 0
URI: http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.js

Message: Object doesn't support this property or method
Line: 212
Char: 7
Code: 0
URI: http://rc/geslic/jquery/jquery.mb.containerPlus.2.5.1/inc/mbContainer.js

What I've Done:

I put your demo jquery.mb.containerPlus.2.5.1 in a webserver IIS 6.0, and rename the file demo.html to demo.asp

I tested it with Mozzilla and it's ok but with IE8.0 I received these errors.

i think i read that IE has a problem with jQuery and appendChild(), you can try to use document instead (adding js-files or css maybe) or the best way, ask the searchengine of your choice against body ie error appendchild by example

hth Abu