When creating a new blog entry with an illegal character (such as &) in the title, and then selecting Preview, a message is produced:

The title you have entered contains invalid characters (:, @, /, %, \, &, !, |, #, $, *, ;, ~, [, ], (, ),

{, }

, <, >).
You should go back to the previous page, edit it and correct the page title in the link.

Unfortunately clicking back on the browser causes it to return to a blank page, and the carefully created insightful blog entry is gone.

I reproduced this problem using both IE and Firefox under windows XP.