I uninstalled the Ender Client and then attempted to reinstall it from the link in the OP. It didnt work. Here's the error messages I got:
<?xml version="1.0" ?>
<jnlp spec="1.0+" codebase="http://dl.dropbox.com/u/18779594/salem/" href="updater.jnlp">
<information>
<title>Custom Salem Updater</title>
<vendor>Ender</vendor>
<description>The Salem game</description>
<icon href="http://plymouth.seatribe.se/java/icon.gif" />
<shortcut online="false">
<desktop />
<menu submenu="Custom Salem Updater" />
</shortcut>
</information>
<security>
<all-permissions />
</security>
<resources>
<java version="1.6+" max-heap-size="512M" />
<j2se version="1.6+" max-heap-size="512M" />
<jar href="updater.jar" />
<property name="haven.defserv" value="plymouth.seatribe.se" />
<property name="haven.resurl" value="http://plymouth.seatribe.se/res/" />
</resources>
<application-desc />
</jnlp>
java.lang.NullPointerException
at org.ender.updater.Main.log(Main.java:66)
at org.ender.updater.Main.main(Main.java:29)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.sun.javaws.Launcher.executeApplication(Unknown Source)
at com.sun.javaws.Launcher.executeMainClass(Unknown Source)
at com.sun.javaws.Launcher.doLaunchApp(Unknown Source)
at com.sun.javaws.Launcher.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)