Blogger.com is implementing captcha to prevent creating splogs (spam weblogs). That means if you post to Blogger with BlogJet, you’ll have to logon to your Blogger web admin panel and type in some numbers from picture.
You will not be forced to enter these numbers every time you publish a post – AFAIK, only sometimes. However, there seems to be a bug that makes you pass through the validation process each time you post. Blogger developers know about this and will fix the bug soon.