I couldn’t access to the java console anymore since I upgraded my system to Java 7 ( yes, call me an amateur programmer ). What you wrote about some exception crashing your game lead me to solve my console problem - I just had to enable it through the system configuration panel.
Then I started to play Farmer John and the Birds 4K again. I reached level 22 this time when the game froze, in the middle of this level. The white screen appeared when I scrolled the page containing the applet. Then I opened the java console - a black screen appeared on it ! I waited for a while. The java console came back to normal, but no exception was indicated.
My Windows 7 system is running Java 7 Update 9, 32 bits version. I played your game under Internet Explorer 9. Later this week, I will try it again with Chrome.