You probably have illegal characters of phrases in your message, thats why the security error kicks in.
What is considered an illegal character?
I want to post the contents of this-- Link --into my blog.
I tried copying from the word document on my computer and the same error happened.
I don't want to just have a link because no one follows links.
I narrowed it down to the ' and ' either side of a few words, and replaced them with " and " and then successfully posted my blog
However I cant see anything like that in the text you are copying, so perhaps you can try the same method to work out what's causing it.
I got a similar error recently and just posted my blog in chunks so I could narrow down what was causing the problem (just use the edit blog thing to add the next bit)
I ran out of patience.
I'll just use LM's screenie. Easier than wrestling to make my own.
Are you copy and pasting from that site?
I tried both from the site and from the original word document.