try uninstalling css menu writer from the extension manager, then reinstalling CSS Menu Writer version 2.0.6 that is available from the download center.
In the case of djogrady376174, we had to resort to renaming the configuration folder to un install all extensions, then reinstalling them to resolve the error.
see step 10 of Adobes Troubleshooting tutorial:
tn_15481.html#main_userConfigFolder