Is Blogger making your crazy by not allowing you to comment? I discovered the solution (for me, anyway) on another blog - Kath at Hillside Cottage:
"When you want to post your comment and you choose the Blogger option, to identify yourself, you end up going round in a circle between the sign in page and the comment box. Sound familiar?
The suggested solution was to UNCLICK the "Stay signed in" box and the loop is broken. I've managed to comment without further problems. Give it a try?