It looks like your server unable to handle large amount of data, generated on “Manage categories” page. Please try to uncheck “Javascript-based list of categories on ‘Manage categories’ page” option on General Settings → Appearance page.
It looks like your server unable to handle large amount of data, generated on “Manage categories” page. Please try to uncheck “Javascript-based list of categories on ‘Manage categories’ page” option on General Settings → Appearance page.