There are three discussions of issues that may lead to this message (or a similar one):
Basically, it seems to boil down to three possibilities:
- There is an image in an article that you are trying to edit and save;
- There are certain keywords in the text of the article (e.g., "function", "create");
- There are certain problematic attachments.
For any of these problems, some people report problems while initially creating the article; others can create the article successfully, but if they then try to edit the article, they have the problem.
You can try to narrow down the problem by creating a very simple article, then gradually adding elements (images, attachments, or text) until the problem shows up, each time editing your result after you've saved it to see if it's only a problem the second time.