I have used SEO Ultimate to remove URL bases of the tags. Every time I publish a post, I have to go to the Miscellaneous settings of SEO Ultimate and click Save settings. Otherwise, the tags won't work and just show a 404 page if I try to access the tag. I wonder if it's because of the cache plugin I am using? I was using W3 Total Cache earlier and now WP Super Cache, but the problem's still there.