Try a few basic troubleshooting steps:
– Try deactivating ALL plugins temporarily to see if this resolves the problem. If this works, re-activate them individually (one-by-one) to find the problematic plugin(s).
– If that does not resolve the issue, try switching to the unedited default, core-bundled Theme for a moment using the WP dashboard to rule out any theme-specific issue.
– If above steps do not resolve the issue, try resetting the plugins folder by FTP or PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems (because the hooks remain unless plugins completely removed or some plugins stick around in cached files. So by renaming the folder, you break them and force them inactive).
– If all the above steps do not resolve the issue, try MANUALLY re-uploading all files and folders EXCEPT the wp-config.php file and the /wp-content/ directory from a fresh download of WordPress. Make sure that you delete the old copies of files & folder before uploading the new ones. Read the Manual Update directions first!
– running the upgrade manually via wp-admin/upgrade.php
