Error on Edit Page

[Menta3K]

I created a new site then publish it and everythig was fine
After few days i try to edit it but i got that error in firebug

SB Config is loaded!
Config is loaded!
uncaught exception: Permission denied to get property HTMLDocument.body
[Break on this error] undefined
uncaught exception: Permission denied to get property HTMLDocument.getElementsByTagName

Any idea what mean that? is it file permissions or jus a bug in parsing engine of the sitebuilder ?