You probably have illegal characters of phrases in your message, thats why the security error kicks in.
What is considered an illegal character?
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 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 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.