A few JCAs, including gem twin, as well as Mack (in this post), have mentioned having difficulty posting a comment. After some investigation into this, I was able to track down the following response from Blogger (click here for source):
We're investigating an issue which is preventing login and comment posting for some users, and hope to have a fix released shortly.So for those of you unable to comment at this moment, take comfort in knowing its not you or your computer. Hopefully Blogger can resolve this latest issue quickly.
Thanks for your patience in the meantime. — latest update on Tuesday, May 24, 2011