Hi Maarten,
if you need to , you can ftp the installer off the box, its located at /usr/netscreen/GuiSvr/lib/webproxy/webapps/download/installers/windows
or linux depending on your need.
The webproxy config script is located at /usr/netscreen/GuiSvr/lib/webproxy/conf/server.xml
Please see below a sample config from a box on 2007.3r2
<!-- Server Configuration File -->
<Server port="8005" shutdown="SHUTDOWN">
--------snip --------
<Connector port="8443" maxHttpHeaderSize="8192"
maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
enableLookups="false" disableUploadTimeout="true"
acceptCount="100" scheme="https" secure="true"
clientAuth="false" sslProtocol="SSL" keystoreFile="/usr/netscreen/GuiSvr/lib/webproxy/conf/.webproxy_keystore"
keystoreType="PKCS12" address="127.0.0.1" />
<!-- Define an AJP 1.3 Connector on port 8009 -->
<Connector port="8009"
enableLookups="false" redirectPort="8443" protocol="AJP/1.3" address="127.0.0.1" />
----- snip ------
Please check the ip (127.0.0.1) as well as the ports, you may also wish to double check that the webproxy is indeed running.
Kind regards
Colin