[Resolvido] DIV nao cresce

boas, estou com o famoso problema de uma div ("main_center") nao crescer directamente com as divs filhas.

Código HTML

<div id="main_center">
 <h1>THERMEC 1978</h1> <div id="product_info">
 <strong>Referência:</strong> 31.27.15<br />
 <strong>Nome:</strong> THERMEC 1978<br />

 <strong>Descrição:</strong><br />
 CALDEIRA THERMEC, 1978, 8 TON/H, QUEIMADOR A GÁS CUENOD, CC800 DO ANO 2000
 </div>
 <h2>Imagens</h2>
 <div id="product_img"><a href="images/products/a1cf798dbc8a1472ea463062ce7c33bc.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/a1cf798dbc8a1472ea463062ce7c33bc.jpg" /></a></div>
 <div id="product_img"><a href="images/products/87aeab8386ae9d456d547be175439aa1.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/87aeab8386ae9d456d547be175439aa1.jpg" /></a></div>
 <div id="product_img"><a href="images/products/8dc02a26ce11aa9e7e44ffe5b48cbed9.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/8dc02a26ce11aa9e7e44ffe5b48cbed9.jpg" /></a></div>

 <div id="product_img"><a href="images/products/cf08b353f2eb35392a0820a80b43980b.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/cf08b353f2eb35392a0820a80b43980b.jpg" /></a></div>
 <div id="product_img"><a href="images/products/97d605b27e405ba4912a7504eb50b7d0.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/97d605b27e405ba4912a7504eb50b7d0.jpg" /></a></div>
 <div id="product_img"><a href="images/products/3d2ba2a62b006165f9bc55e4fa39c552.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/3d2ba2a62b006165f9bc55e4fa39c552.jpg" /></a></div>
 <div id="product_img"><a href="images/products/5bbf38fdf05bfb4c1f1fcaf8354f2acb.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/5bbf38fdf05bfb4c1f1fcaf8354f2acb.jpg" /></a></div>
 <div id="product_img"><a href="images/products/38f15d0e16adcc86be85d15c913d4d68.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/38f15d0e16adcc86be85d15c913d4d68.jpg" /></a></div>
 <div id="product_img"><a href="images/products/ba4da8781fd4b7c7d8362f65a46dc3b3.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/ba4da8781fd4b7c7d8362f65a46dc3b3.jpg" /></a></div>
 <div id="product_img"><a href="images/products/c7fc8e000303870045f66b5634502c2b.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/c7fc8e000303870045f66b5634502c2b.jpg" /></a></div>
 <div id="product_img"><a href="images/products/df4329d6d12246a43526ebfda25c7832.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/df4329d6d12246a43526ebfda25c7832.jpg" /></a></div>
 <div id="product_img"><a href="images/products/a7d12ba3a62621b3a34885c886ea072a.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/a7d12ba3a62621b3a34885c886ea072a.jpg" /></a></div>

 <div id="product_img"><a href="images/products/e7f35104486b48af0119c73ec1906de6.jpg" rel="products"><img src="thumbnail.php?thumb=images/products/e7f35104486b48af0119c73ec1906de6.jpg" /></a></div>
 </div>

Código CSS

#content #main_center {

	display:block;
	width:492px;
	background:url(images/main_bg.jpg) repeat-y;
	min-height:470px;
	padding:0 15px;
}

#product_img {
	text-align:center;
	vertical-align:middle;
	width:155px;
	height:115px;
	float:left;
	margin:3px;
}

#product_imgs {
	float:left;
	position:static;
	display:block;
}

#product_info {
	float:left;
}

para verem melhor o prob, deixo aki o link: http://www.natcal.pt/new/?s=cHJvZHVjdHM=&mode=dmlld19wcm9kdWN0&u=2