I don't get that warning when using the WYSIWYG editor. But I do know that I can't right-click to "select all" the text. Instead I have to use the button specifically for it in the editor. If you switch to the text editor, of course, you can right-click, select all and copy, but you get all the code as well.
Oh, and for the most part Firefox works great for me as well (on XP).