drupal.js is loading before jquery.js I have face this problem often in my drupal site. The drupal.js file is loading before jquery.js, so i get the "uncaught jQuery is not defined" error.

I have been using memcached also in my site.

But I can fix the error by the following steps


Restart memcached
Restart Apache
Cache clear
Run the cron


After doing the steps the jQuery is loading properly.

Now, i want to know the reason why the drupal.js loading before jquery.js?

FYI : This is happening, When I enable/disable any modules/features through UI
May be because of cache that might cause 


Check if you installed jquery_update module 
in themes info check if there you have declared jquery

3.check if in any module hook_init() you are adding your js with weight. 


if you install jquery update module you dont need to add jquery plugin in info file 

if you have any clarification regarding the js weight and so on read the following links will be helpful 

https://www.drupal.org/node/756722

https://www.drupal.org/node/304255