Credo di aver individuato l'errore. Cambia il src="" dell'embed con quello che inserisco io in grassetto:
codice:
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,0,0" WIDTH="186" HEIGHT="33" id="form0" ALIGN>
<param name="_cx" value="4921">
<param name="_cy" value="503">
<param name="FlashVars" value>
<param name="Movie" value="newsletters/formnews.swf">
<param name="Src" value="newsletters/formnews.swf">
<param name="WMode" value="Transparent">
<param name="Play" value="0">
<param name="Loop" value="-1">
<param name="Quality" value="High">
<param name="SAlign" value>
<param name="Menu" value="-1">
<param name="Base" value>
<param name="AllowScriptAccess" value="always">
<param name="Scale" value="ShowAll">
<param name="DeviceFont" value="0">
<param name="EmbedMovie" value="0">
<param name="BGColor" value="FFFFFF">
<param name="SWRemote" value>
<param name="MovieData" value><embed src="newsletters/formnews.swf" quality="high" bgcolor="#FFFFFF" WIDTH="255" HEIGHT="25" NAME="form" ALIGN TYPE="application/x-shockwave-flash" PLUGINSPAGE="http://www.macromedia.com/go/getflashplayer">
</object>