Bumping this thread, because I just got an N800, and the situation is the same.
Fresh Diablo. Installed mc and rootsh from the repositories.
xterm, sudo gainroot, mc, and used mc to copy install-tools-ad.tgz from my card to /root.

The next step,
tar zxvf install-tools-ad.tgz
gets me
tar: invalid gzip magic
I'm sure I'm missing something obvious.
What is it?