You can try it on the test page:
http://tinymce.moxiecode.com/example.php

If you paste an URL in FF it will remain in plain text, but if you do it in IE TinyMCE will append an anchor tag to the link.
This poses a problem when combined with other filters like urlfilter, googtube filter etc.

I already tried to set convert_urls to false but it has no effect.
Does anyone know how to disable automatic link conversion in IE?