I have tried to allow write access on the C:\Users\ann\AppData\Local\Temp\1 folder without success. In debug mode, it doesn't crash but doesn't show where the error occurs.
Windows 10 Pro x64, jdk 8u74, B4J 4.20
Now I do have another "something else strange". Even if I change the client's package name, I get this in the logs Class not found: b4j.cloudkvs.server.main$_item, trying: b4j.sample.main$_item but the server is not running on the machine and the code is just what was downloaded, only the IP was changed. Saved twice the project but no update