I've had this before, when it happens I usually turn down the process priority in task manager for the java.exe process which is using the most CPU (the installer starts two java.exe processes). It might not work for you, but it's worth a shot.
I've not heard of "us-en" being a requirement to install, in fact the default locale I use is the UK one, and I usually uninstall the US locale when I first install the OS. I remember this applied to certain products for LC7, but it's not been something I've had to worry about with ES.
A side issue (probably unrelated), when you say "latest JDK", I think ideally it would be a Java 5 JDK, not the latest major version, 6. From the "System prerequisites" section of installation docs:
Sun Java Software Development Kit (JDK) 1.5.0_11 or a later update of JDK 1.5.0.