blockquote's strange behavior

When i press on the blockquote button, the editor insert's HTML in this form:

<blockquote>
<div></div>
</blockquote>

and places the mark after the div element.
first of all, why does the div is inserted too?
second of all, in IE it looks like the blockquote got two rows and the mark is at the second row, but in FF it seems like there is nothing there!
how can i fix it?
thanks in advance.