ok.. I think my fault..
I didn´t put in the CSS-Code.. now the viewer.swf shows up.
Update: Well, I solved my problem. I´m now using the way for myspace, but of course in the xhtml-correct way, because "embed" is naughty.
<p><object width="550" height="400" data="/path/viewer.swf" type="application/x-shockwave-flash">
<param value="/path/viewer.swf" name="movie" />
<param name="FlashVars" value="xmlDataPath=/path/gallery.xml" /> </object></p>
Now, Simpleviewer doesn´t have problems to find the XML and the images folder.
Finally I can start to cook and watch MST3K.. goodnight people.