Originally Posted by Manichean
Nope, that didn't fix it. If it helps, I get the same error regardless of whether the tweak is set or not.
Hmmmm that sucks. Can you open the plugin zip file in your Calibre roaming folder (get to it via Preferences->Advanced->Miscellaneous->open calibre configuration directory, then in the plugins subfolder). Check that it really does have the latest code in there with these two lines at line 44:
search_internet_menus = None