<blockquote>ja erio supports flash?</blockquote>
You must insert the correct code in your custom-html module to have the flash showed correctly something like this
<object height="yourheight" width="yourwidth" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=10,0,32,18" classid="clsid:d27cdb6e-ae6d-11cf-96b8-444553540000">
<param name="wmode" value="transparent" />
<param name="src" value="images/stories/swf/yourfile.swf" /><embed height="yourheight" width="yourwidth" src="images/stories/swf/yourfile.swf" wmode="transparent" type="application/x-shockwave-flash"></embed>
</object>
and check if your editor doesn’t clean your html code when you save your module ( in other words after saved the module check if the code inside is still the same you inserted before )