For those having difficulty:
1. Go to my NS > Accout Tools and click yes for the Fancy Editor (if your not using it already)
2. Click the Flash symbol (script f in a circle) when you have the message reply box open ready to make a post
3. Try pasting only the embed portion of the code into the box. For example:
<embed src="
http://www.youtube.com/v/cqi5F5MqqTQ&rel=1" type="application/x-shockwave-flash" wmode="transparent" width="425" height="355"></embed>
instead of
<object width="425" height="355"><param name="movie" value="
http://www.youtube.com/v/cqi5F5MqqTQ&rel=1"></param><param name="wmode" value="transparent"></param><embed src="
http://www.youtube.com/v/cqi5F5MqqTQ&rel=1" type="application/x-shockwave-flash" wmode="transparent" width="425" height="355"></embed></object>