I just enabled networks on my WP3.0 site, only to find that my permalinks for the main site now include blog/ in all post URLs. For example, previously, my posts used to be domain.com/2010/08/01/post-title/; they are now domain.com/blog/2010/08/01/post-title/. Oddly enough, the categories still have my custom modifier; domain.com/category/cat-name/ is still used, not domain.com/blog/category/cat-name/. In addition to categories, pages are also still fine (domain.com/about/, not domain.com/blog/about/). I updated to 3.0.1 after activating multisite, and the issue persists.
In permalink settings on the primary site, blog/ shows up as an unconfigurable prefix in front of my permalink choices. On all additional sites, everything works fine.
I do not have a site, category, tag, or anything else called "blog" so I'm not sure where it comes from. Any guidance is much appreciated, thanks!