Presently Drupal 5.X and 6.X have intermittently broken behavior with a hand full of TinyMCE features. Some of these feature inconsistencies have to do with tags that are disallowed by default (like the image align tag). I believe my example Drupal installation is experiencing an unrelated problem.
I am wrestling with the table feature and its inconsistent behavior when pasting text into a field (using the text past feature or the Word [cleaner] paste feature). The table seems to be very unstable (in the interface) and throws odd code in when I paste any text into any cell. This is plain ascii text, even using the little text pasting tool in the WYSIWYG. Oddly, testing this on non-Drupal installations of the WYSIWYG does not yield the same result. TinyMCE seems to be relatively stable by itself. It seems that it is a Drupal filter or javascript behavior interference. I assume it's a generic Drupal-wide filter I've yet found.
I'm posting my experience with this problem for your view (video).
If you know about the Drupal filters, or have a solution, your feedback is much appreciated.
My video example: http://ns.silohost.com/~jason/drupal_table_tinymce_problem/drupal_table_...