Ok, after a reinstallation I got this to work at least partially. This is pretty crazy as I have never tampered in any way with my installation folder.

@Rojart: Thanks, you're right, the mode keyword has to be there.

@jcl: Could you please update the manual, because
Originally Posted By: Manual
WINDOW WINSTART { ... } [...] If the brackets are empty, no start window will be displayed.
is wrong. The brackets must not be empty.

The generation of a .wdf file unfortunately only works from the command line for me. When publishing from SED I still get the same error messages.

Always learn from history, to be sure you make the same mistakes again...