The only other thing I can think of is to try and use the new 1.6b beta version of Java. But then you should first uninstall the other Java version(s).
http://java.sun.com/javase/6/download.jsp
That it is a general problem of the 4.12.3 version of LW I rather doubt, since I'm running this very version daily on my computer without any problem.
So, it must be somehow connected to other things you have (or you do not have) installed on your computer.
And since you saidd you read through the thread of LOTR and tried ALL his suggestions (which should include to check-update-reset your graphic card driver(s) ), I'm running out of ideas.....
