I had the same problem. If you try to open the zip file "eclipse-java-galileo-SR2-win32.zip" in jbpm-4.4\install\downloads folder, you will see that the file is damaged.
I solved the problem by changing the property name="eclipse.distro.url" in the build.xml file - see install folder.
Change the URL to one of available mirrors. Just open the current URL in the browser and select a mirror. Copy and paste the URL.
Afterwards the eclipse download works.