Just after installing eclipse from lenny repository, it crashed me up with the error JVM terminated. Exit code=127. After a bit of searching and watching at what a console execution told me, I tried execute eclipse from command line with a simple java -jar /usr/lib/eclipse/startup.jar. Well, in this way it starts up successfully without any problem. Then I tried again a startup from gnome menu and everything worked fine.
Now there is still the failing about integrated browser and the fact that eclipse shipped with lenny is the very obsolete 3.2.