Q:

Why my Expression Engine default menus don't load?

I was running 2.6.1 and I logged in today (hadn’t logged in since june 2013), none of the EE menus are working.  All the menus and buttons at the top do not work anymore.  I upgraded to the latest version flawlessly but yet still none of the buttons or menus are working.  It’s like the AJAX/jquery or whatever they use to show the menus isn't being loaded.
The sidebar will not expand either.  The menus at the bottom of the control panel EE Info, Learning EE, News and Stats, & quick tips wont expand either.
When I edit an Entry none of the buttons work there either, ie: publish, date, ping, pages, revisions, etc.
They all load but there is no effect when I click on them.  Yes I have tried uploading it all again.  I even uploaded it and tried it as fresh install (as a new site) and they still didn't work. I have tried it on IE, Chrome, Firefox, Safari. None of the menus works.  It doesn't make any sense to me really.

A:

Ok this is the solution I finally found thanks to Ellis Lab and my webhost Eleven2. Ellis Lab discovered it was a 403 issue doing some testing on my account and I passed along the information to Eleven2 and they fixed it with the solution below. I hope this helps anyone else hosting on Eleven2 or anywhere else that's having this problem.
It was an issue with the mod_security.
You can give the following lines in the .htaccess file of the account to fix the issue.
<IfModule mod_security.c>
SecFilterEngine Off
SecFilterScanPOST Off
</IfModule>

