Can the <script> tag not be self closed?

I had this code in my website

<script type="text/javascript" src="http://code.jquery.com/jquery-1.4.4.min.js"/>
<script type='text/javascript' src='/lib/player/swfobject.js'></script>

swfobject was not working (not loaded).

After altering the code to:

<script type="text/javascript" src="http://code.jquery.com/jquery-1.4.4.min.js"></script>
<script type='text/javascript' src='/lib/player/swfobject.js'></script>

It worked fine.

The document was parsed as HTML5.

I think it’s funny. Okay, granted a tag that is closed and a self-closing tag are not the same. So I would understand if jQuery couldn’t load (although I find it ridiciulous).

But what I do not understand is that jQuery loads but the following, correctly written tag, doesn’t?