Pasting into the editor from a rich text file doesn't work

In our application we force all users to use the "paste as plain text" dialog window in order to strip out problematic characters. This works with most text files, including pasting from Microsoft Word, but if you are pasting from a rich text file it still allows problematic characters into the editor.

Paste from a rich text file, save it to the database, then try to load the page again initializing the editor with the text you just saved. The editor won't even load because all sorts of problematic characters.

Anybody know a way to handle pasting from rich text files?

Thanks!