I've just resolved a rather frustrating bug preventing many people from posting on my blog (thanks for pointing this out Margaret).
When trying to comment, a little pull-down menu asked users to "Choose A Profile" and sent many on an infinite loop of login and verification requests.
For others experiencing the same problem, here’s my solution:
In your blog SETTINGS, under the COMMENTS tab, you have three choices for how your comments will appear (Full Page, Pop-Up Window, or Embedded Below Post). The problem is in the third, default, choice - Embedded Below Post.
Select one of the other two options and the issue should be resolved. I've changed mine to "Full-Page".