I have updated the betashot applet to a none proguarded version, should be easier to follow those exceptions (although has added a 100kb to it ), Riven could you try again please and post the console output?.
Also for those that had the problem with it only working the first time and thereafter failing, I have uploaded a no cache version, can you try it and see if you still get the same problem http://kappa.javaunlimited.net/betashot4/betashot-nocache.html
I have not been able to reproduce the error, so still unsure why it works for some computers and not yours, doesn’t seem to be any link with jre versions although does look like it only happens on windows, if the above no cache applet starts working for you than it should get me a step closer to figuring out where the problem is.