Drag and Drop Widget not working

Have you tried:

– switching to the default theme to rule out any theme-specific problems.

– resetting the plugins folder by FTP or PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems.

– re-uploading all files & folders – except the wp-content folder and wp-config.php & root .htaccess files – from a fresh download of WordPress. Make sure that you delete the old copies of files & folder before uploading the new ones.

I had this problem too.

I did a clean, plain install of 3.7.1 on a test domain and verified that the problem isn’t WordPress itself.

Doing a binary search through all my plugins found the culprit in my case (the BlazeMeter plugin).

I deactivated all my plugins and confirmed that this solved the problem. Reactivated half of them, found the problem didn’t come back, so kept reactivating half the remaining plugins until the problem resurfaced. Then it was easy to figure out which plugin was causing the issue.

I think kmessinger’s advice is good.