Troubleshooting 101:
1. Disable all plugins. Does the issue persist? If yes, continue to step 3.
2. If the problem has disappeared after disabling all plugins, slowly start to re-enable your plugins, one by one. If the problem shows up, remember the last plugin you enabled, check to see if there’s an update for the plugin and if not, contact the plugin developer and let them know that there may be an issue with their plugin. Tell them the steps and the environment (server, WordPress version, plugins, themes, etc.) to reproduce the issue.
3. Enable a default WordPress theme (Twentytwelve or Twentythirteen). Does the issue persist?
4. If the issue is gone, then the issue is *likely* in whatever theme you were using before enabling the default WordPress theme. Check to see if there’s a theme update for your custom theme. If not, contact the theme developer and let them know the steps to recreate the issue and see if they’ll update the theme. If not, consider finding a new theme or, if you’re into PHP and WordPress development, consider digging into the theme yourself to fix it (assuming you have the rights to do that).
5. If the problem still persists after all the above, consider manually updating your WordPress install by uploading the latest WordPress files to overwrite your existing files with the exception of wp-config.php and the wp-content folder. This should likely resolve any lingering issues. If not, post back here again and let us know what steps you’ve taken and we’ll go from there.