Using flash in posts

I am having trouble inserting flash into my blog when i add the code <object width="425" height="350"><param name="movie" value="http://www.youtube.com/v/aeXAcwriid0"></param><embed src="http://www.youtube.com/v/aeXAcwriid0" type="application/x-shockwave-flash" width="425" height="350"></embed></object>
to my post it breaks the page and when i go to have a look at the code in the post it has been shortened to this:
<object width="425" height="350" />
<param value="http://www.youtube.com/v/aeXAcwriid0" name="movie" /> which is why it seems to break the page.

Is there a diferent code I need to user to insert flash into a post or am I doing something else wrong?