Java Web Start update wrong Java version

I am using Java Web Start for over a year now and it worked fine, but since today you get redirected to the Java 7 download page instead of starting our application.

Is there any way to provide Web Start with a maximum Java version? Do you have any ideas how to get rid of the forced Java 7 update? With Java 7 the software do not start.

Here is the code of the web page:

...
<script src="http://www.java.com/js/deployJava.js"></script>
<script>        
    var url = "http://SOME_IP/app/vabnet.jnlp";
    deployJava.createWebStartLaunchButton(url, '1.6.0');

</script>
...

And here is my jnlp file:

?xml version="1.0" encoding="UTF-8"?>
<jnlp spec="1.0+" 
    codebase="SOME_URL" 
    href="vabnet.jnlp">
    <security>
   <all-permissions/>

</security>
    <information>
        <title>VABnet</title>
        ...
    </information>
    <resources>
        <!-- Application Resources -->
        <j2se version="1.6+"
              href="http://java.sun.com/products/autodl/j2se" 
                    initial-heap-size="256M" max-heap-size="256M"/>
        <jar href="VABnet-Client.jar" main="true" />
        ... some nativeLibs
    </resources>
    <application-desc
         name="VABnet"
         main-class="de.vab.vabnet.client.application.VABnetLauncher"
         width="300"
         height="300">
     </application-desc>
     <update check="background"/>
</jnlp> 

I am sure nobody has changed the content of the web start folder inside the Apache folders. Thanks in advance ...

UPDATE: I have found one computer in our company where it still wokrs without getting redirected to the Java 7 download page (the first four computers which I had tried had all redirected me). Now I try to check the configurations of Java Web Start.