Oops, it looks like your java's broken indeed. Do you actually see anything
under /usr/lib/j2se/1.4/jre/ ? That's where the BlackDown jre lives.
I don't know what the debian package name would be to install using apt-get.
I suggest you download 1.4.2 from Sun instead. Choose the plain jre/jdk
(your choice) rather than the netbeans co-bundle. The latter wouldn't install
under debian for me. Netbeans is available separately if you want to compare
it to eclipse.

Cheers,

--bald.