This evening I found myself unable to sign in to and leave a comment on my own blog. After struggling with it for over a half-hour, I switched this blog's "Comment Form Placement" to "Full Page" from "Embedded." That seems to have circumvented the commenting problem, but I still can't edit my own blog.
If you've tried to leave a comment recently - the past two or three weeks - and were unable to do so, please try again.
Others have reported the same problem in the Blogger Help forums, but no one has gotten any relief.