Ive had the same problem, and here is a workaround that should work for you:

Go to 'user manager' and choose a user that is editing the content.  Under 'parameters' switch off the tinymce editor i.e. select no editor.

Youll see the HTML code directly in the Article and  paste your code as above.

Save the article.

Go back and switch tinymce back on.

But, when I want to embed a media flash player, using <div>..</div> the tinyMCE has clear my code.

For example:
I want to insert

<embed flashvars="width=650&amp;height=490&amp;displaywidth=524&amp;autostart=true&amp;file=/201105/13851_redridinghood2011vcd.flv&amp;streamer=http://vip.phimhbo.com/ctl/video/?bts=vs.forum&amp;backcolor=0x000000&amp;frontcolor=0xCCCCCC&amp;lightcolor=0x557722" allowfullscreen="true" allowscriptaccess="always" quality="high" src="http://megafun.vn/common/v2/player/player.swf" type="application/x-shockwave-flash" height="490" width="650">

but when i click submit, It's begin:

<img _mce_src="media/editors/tinymce/jscripts/tiny_mce/plugins/media/img/trans.gif" src="media/editors/tinymce/jscripts/tiny_mce/plugins/media/img/trans.gif" width="650" height="490" style="" _mce_style="" class="mceItemFlash" title="&quot;flashvars&quot;:&quot;width=650&amp;height=490&amp;displaywidth=524&amp;autostart=true&amp;file=/201105/13851_redridinghood2011vcd.flv&amp;streamer=http://vip.phimhbo.com/ctl/video/?bts=vs.forum&amp;backcolor=0x000000&amp;frontcolor=0xCCCCCC&amp;lightcolor=0x557722&quot;,&quot;src&quot;:&quot;http://megafun.vn/common/v2/player/player.swf&quot;,&quot;allowfullscreen&quot;:&quot;true&quot;,&quot;quality&quot;:&quot;high&quot;"></p>

please help me! How to keep current html custom of mine ?