Problem when inserting a SWF only

Hello, I have the following problem:

When I insert a SWF file (and nothing else) into the editor, it won't get displayed unless I insert a space before the SWF or some other text after it.

When I click the Source button, no code is displayed and the flash logo gets deleted.

It looks like the editor does not like it if there is only

<embed type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer" src="/userfiles/buton.swf" play="true" loop="true" menu="true"></embed>