Use the option 'use old embed code' on youtube and then add this inside object -
<param name="wmode" value="opaque"></param>
That will set the Flash z-index lower.
<object width="420" height="315"><param name="movie" value="http://www.youtube.com/v/G2zpWw_0Er4?version=3&hl=en_US&rel=0"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param>
<embed src="http://www.youtube.com/v/G2zpWw_0Er4?version=3&hl=en_US&rel=0" type="application/x-shockwave-flash" width="420" height="315" allowscriptaccess="always" allowfullscreen="true"></embed></object>