In Chrome when the window that contains the applet is resized then the applet freezes. The cause of it is JavaScript communication between applet and browser. It also happens on your demo page (http://www.jfileupload.com/products/dem ... jsapi.html).
My configuration is:
Win 7 x64
Chrome 39.0.2171.65 m
JRE 1.7.0_71-b14