In my opinion, your IE6+sp1 is using Java Sun Virtual Machine, and Keai's applet might dislike this setting, and that's why
I recommend you using Microsoft Virtual Machine to test.
IE6 itself has no Java Virutal Machine built in, so you have to download yourself, either Microsoft VM or Sun's Java. I am not sure where you get your Java 2 v1.4, maybe your download from Sun's site? Or you might get Java 2 v1.4 from IE6 sp1.
MS has an agreement with Sun on the java standard. MS basically will stop support Microsoft VM and use Sun's stuff instead. However many java applets were actually written by Microsoft J++, and some of them unfortunately will not correctly in the Sun's Java VM.
By the way, are you using windows XP, I found this problem only happen on XP, not windows 2k.
I am not sure where you can get a MS VM, maybe you can try install J++ on your machine. However I do found that some applets only work in MS VM.