JDownloader doesn't start despite several new installs and/or deletion of cfg folder:

Log:

org.jdownloader.update.launcher.JDLauncherFailedException: java.lang.NoClassDefFoundError: org/jdownloader/startup/Main
at org.jdownloader.update.launcher.SecondLevelLauncher.launchJDownloader(SecondLevelLauncher.java:602)
at org.jdownloader.update.launcher.SecondLevelLauncher.init(SecondLevelLauncher.java:465)
at org.jdownloader.update.launcher.SecondLevelLauncher.runMain(SecondLevelLauncher.java:267)
at org.jdownloader.update.launcher.JDLauncher.main(JDLauncher.java:19)
Caused by: java.lang.NoClassDefFoundError: org/jdownloader/startup/Main
at org.jdownloader.update.launcher.SecondLevelLauncher.launchJDownloader(SecondLevelLauncher.java:583)
... 3 more
Caused by: java.lang.ClassNotFoundException: org.jdownloader.startup.Main
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 4 more