If you are using any SEO Extension which can generate meta titles in bulk, then you may need to disable the required field of meta title in the product / category / information / manufacturer catalog form pages. Because you will not be able to save the form without filling this field.
To be used only if you use any SEO extension and which doesn't disable it already by the SEO extension.
Two versions available for this add-on
To install vqmod version, extract the contents inside the upload folder to your root directory such that the xml file of this extension gets placed in vqmod/xml folder.
To install ocmod version, find the file with .ocmod.xml extension and upload this file using your admin : Extension > Extension Installer.