For some reason some files in my CVS checkout sometimes end up without write-permissions for myself. I can easily change them in emacs shell buffer, but if they’re already open in emacs, I still get <buffer is read-only> nags. Here’s how to get rid of that: meta x toggle-read-only or C-x C-q.

Thanks to Andrew Grumet and blighty at #openacs who helped me out with this.