Then sign back into Blogger on the front page, go back to your blog, and you should be able to post and publish once again. Previously, you could have misspelled tags, improper nesting, unknown tags, etc, and it wasn't a problem. The new system, however, requires that all tag syntax and placement is correct before it allows you to publish. There you will find a list of all the available tags. There is also a link to the default template if all else fails and you cannot find your problem.
Proper capitalization is also very important.
Simply delete the tag from your template to solve the problem. If none of that works, post to this thread and we'll get on it. Go to your archive settings, and change your archiving frequency to No Archive . Save your changes and publish. Then go back to your archive settings again, and select the monthly or weekly option you had previously.