JQuery problem with 2.6.1 (4 replies)

Hello,
I have Piwik running into Ubuntu Server 12.4.5 LTS with PHP 5.3.10.
After updating to 2.6.1 report pages are empty and console javascript (Firefox 32.0.1) says "ReferenceError: $ is not defined index.php:58"
I tried to extract the installation manually in a new folder using the old same database, but it didn't solved. I also cleared cookies and browser cache.

Any suggestions?