When the JVM argument -XX:+UseCompressedStrings is specified, the wrapped application fails to start - appearing to terminate silently.
Versions used: Launch4j 3.0.2, Java 6u25, on Windows 7 x64
I notice that this JVM flag has been dropped from Java 7. (Which is a shame, as it made quite a big impact on my little application.) I guess it must have caused too much trouble to continue to support, or it was too dodgy..
Works here, for launch4j it's an option as any other, so perhaps the problem is because of the dropped support. If you still have problems with it please reopen the ticket and include the --l4j-debug output.