Couple things:
1) I'm uploading a new one that won't have this problem -- give this about 10 mins

2) If you have 1.4 installed, but you run jEmplode with the executable, you are actually only using 1.3 (the VM that it comes with -- which is why this problem occurred). Instead, you should double click the jemplode20-supersecret.jar or run "java -jar jemplode20-supersecret.jar").

Oh yeah -- one other thing -- you may want to turn off autoupdate, since 42 will try to "update itself" to 41.