
These bX errors are caused not only when you are editing template but also when uploading picture, editing profile or choosing a wrong setting. Here are six possible solutions over this problem.
1. Change the browser. Simply, try the same thing from different browser (Opera recommended)
2. Delete all the widgets of your current template before uploading a new one (ofcourse, make a backup).
3. Delete Browser cookies and try again.
4. Remove widget codes manually of the template you are trying to install. For example : from
5. Just wait for sometime and try later.
6. Contact Blogger if it continues.