jQuery Problem in Admin pages after Server Upgrade

Hello everyone,

I’m running two WordPress sites, and after a server upgrade last weekend which included moving all files I’m facing a Java Script problem on one of them backend, solely in the admin area.

The problem occured first, when I attempted to control settings in a security and firewall plugin: I could access settings with my password, but wasn’t able to activate any tabs but the first one. Instead of leading me to the section I chose, let’s say the general plugin options, it added the line #pills-section_general_plugin_options to the url which brought me nowhere.

Secondly I realized that the statistic tool didn’t show any informations. In each and any field the spinning wheels continued spinning, but that was it ad infinitum.

The menu items on the left side of the admin pages won’t show submenus until I click them, etc.

This morning I received a warning generated by the security plugin that its Core File Scanner has found 4 core files which don’t match official WordPress files:

– wp-includes/js/zxcvbn.min.js
– wp-includes/js/mediaelement/mediaelement-and-player.min.js
– wp-includes/js/codemirror/csslint.js
– wp-includes/js/plupload/moxie.min.js

The plugin has replaced these files with the original WordPress files, but the unusual behaviour described above continues.

I turned on script debugging and the issues were fixed. I turned off script debugging and opened the Error Console in Firefox which listed countless Reference Errors “jQuery is not defined”.

And since I’ve no clue what all this means I’m wondering if I shouldn’t delete everything and start with a fresh WordPress installation.

Any help to avoid that would be most welcome.
Thanks in advance!