WP: Why does the last line of a sIFR blockquote have double line-height?

Question

Hi,

I currently have the following issue:

http://img833.imageshack.us/img833/2654/downloadf.jpg

I've been tooling around with the CSS but can't get ride of the issue. I think part of the problem is that WP automatically gives out P tags (which I'd also like to retain for usability, i.e. not disabling this in the WYSIWYG), i.e. the final code is as such:

<blockquote><p>Cras quis nisi lorem. Vestibulum quis tortor mi, ut iaculis massa.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Curabitur mauris elit, facilisis quis dapibus id, iaculis sit amet nunc. Nam et justo non velit sodales venenatis sit amet ac ipsum. Duis posuere blandit euismod. Donec sit amet augue lacus.</p></blockquote> 

And the relevant CSS is as such:

.post p {
 line-height:18px;
 margin:18px 0 0;
}
.post blockquote {
 background:url(../images/quote.gif) no-repeat 3px 3px;
 font-size:18px;
 line-height:18px;
 font-style:italic;
 color:#485f62;
 overflow:hidden;
 padding:0 0 0 30px;
 margin:18px 0 0;
}

.post blockquote p {
 line-height: 18px !important;
}

* html .post blockquote {
 height:1%;
 overflow:visible;
}
.post blockquote q:before, .post blockquote q:after {
 content:"";
}
.post blockquote q {
 quotes:none;
}

Many thanks in advance for any help you can provide :)

(I am using WordPress 3.01, WP sIFR)