The overlaps doesn’t work with z-index, the only way is put in the two parameters “&wmode”:
&wmode=Opaque &wmode=transparent
Example:
<iframe title="YouTube video player" width="480" height="390" src="http://www.youtube.com/embed/lzQgAR_J1PI?wmode=transparent" frameborder="0" wmode="Opaque">
What do you think?