My current analysis:
With java7u7 does not work any more, with java 6 is still works.
I have done a java update from system tool, it looks like it does not update the jdk.
But even after remove all java7 and reinstall them, adjus PATH and JDK_HOME, it does not work.
I also removed the temporary java files with the java control panel in the windows settings.
I also tried to call javaws.exe it from the command line. Without options, it shows an info box, so at least this works.
But with "javaws.exe -verbose downloaddir\launchdevui.jnlp" it crashes before it can produce any output.
When I use a still installed java6u33 from the command line, it works.
One possible problem with RDA and Java7 is the following:
\java\java6\jre\javaws.exe -verbose downloaddir\launchdevui.jnlp
The codebase attribut the jnlp-file should now use "https" instead of "http",
according to this stack-overflow entry: