You do not want to use a frame busting script in the template of a Blogger based blog.
It will disable your ability to use the upper toolbar in the layouts mode, and you will not be able to access the HTML of your template without a bit of "URL hacking" to get to it.
If you have added it and can't access the HTML of your template, just change the layout URL, replacing the word "display" with "html".
change this: http://www.blogger.com/display?blogID=12345678
to this: http://www.blogger.com/html?blogID=12345678
Now you can find and remove the frame busting script and everything will work normal again.