Java Web Start 1.5 lost the possibility to adjust proxy settings 
independently from Java Plugin. This was possible for Java2SE 
1.4.2 (and earlier).

1. Java2SE 1.4.2
----------------
1.1 Java Web Start
------------------
For Java Web Start 1.4.2 it was possible to adjust Proxy settings 
in "Java Web Start Application Manager":

"c:\j2sdk1.4.2\jre\javaws\javaws"
File -> Preferences -> General -> Proxies
 (x) Manual
 adjust Proxy host, proxy port and no-proxy list

For Java Web Start the following properties are written in file 
"deployment" properties:

deployment.javaws.proxy.settings=MANUAL
deployment.javaws.proxy.http=<fully qualified proxy-host>
deployment.javaws.proxy.httpport=<proxy-port>
deployment.javaws.proxy.httpproxyoverride=


1.2 Java Plugin
---------------
For Java Plugin 1.4.2 the proxy configuration was done in the
"Java(TM) Plug-in Control Panel" (in Windows Control Panel)
on the "Proxies" tab in the "Protocol Address Port" table.


For Java Plugin the following "deployment" properties are written:

javaplugin.proxy.settings=http\=<fully qualified proxy-host>\:<proxy-port>
javaplugin.proxy.usebrowsersettings=false
javaplugin.proxy.bypass= 


So, in Java2SE 1.4.2 Java Web Start and Java Plugin could have proxy 
settings independently from each other.


2. Java SE 5.0
--------------
Beginning with Java SE 5.0 the "deployment.javaws.proxy.*" properties 
do not seem to be regarded any longer.

The "Java Plug-in Control Panel" became the "Java Control Panel", 
where Proxy settings can be made in 
Java Control Panel -> General -> Network Settings 
 (x) Use proxy server

For Java Web Start the "Java Web Start Application Manager" became 
the "Java Application Cache Viewer" and is called via 
"c:\jdk1.5.0\jre\bin\javaws". 
The Edit->Preferences dialog now directly calls the 
"Java Control Panel".

So, there is but one unified place for proxy configuration settings.