That is the error message I get Dot. As Lance and Heather has demonstrated it probably comes down to a word or combination of words. It would be interesting to see if you could narrow down the cause. You can just do it by clicking the 'preview post' button so that you don't keep actually posting. You should be able to narrow it down to a sentence or a few words.I ultimately got around it by breaking my post up into two part. Why? I have no idea.