Cannot open URI despite DesktopAPI is supported

[cmos]

I try to open a local XML-based file in the system-default browser using the DesktopAPI. Since the code works fine on a Windows machine and I use a Kubuntu with KDE 3.5, I supposed that the code didn't work for me due to lacking support of the DesktopAPI.
Well, the DesktopAPI seems to be supported. Also I can open "usual" URLs (like clusty.com) with the same code.

Stacktrace:

java.io.IOException: Failed to show URI:file:///home/kaptain/runtime-EclipseApplication/Test/DefaultArtifacts.wsdl
	at sun.awt.X11.XDesktopPeer.launch(XDesktopPeer.java:75)
	at sun.awt.X11.XDesktopPeer.browse(XDesktopPeer.java:64)
	at java.awt.Desktop.browse(Desktop.java:368)
	at ise.discovery.ui.texo.view.detail.impl.HTMLDetailView.open(HTMLDetailView.java:101)
...

So the browser can be found and it can open www URLs, but not URIs to local files. Is there sth. I can do about?