One possible cause of not being able to use Discoverer ...

If your Java Control Panel looks like the following you will need to download and install the JDK toolkit. Also, it is important to disable automatic updates here as you do NOT want Java to update to the most recent version, 1.6, as Discoverer and Java 1.6 will not work together. In order to be able to see the “Update” tab of the Java ... ................
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