Ok... not sure how I can try it...
As the steps to reproduce would involve... pre population of the ce area with the html, and adding the styles to the external wysiwygcss file??
If I move to html and paste my html, and move back I've already done what I've found fixes it... and there is no way I can add a style definition to your external css??????
Basically to test requires access to your server and code!
If you like I could give you acccess to our server so that you can see what is going on.... if you provide your ip I can grant you access to one of our developement sites.. and set up two pages one with the error and one with the altered css?
Mike