You might need to edit /dev/sdb1 of the /etc/fstab of Ubuntu and then mount it. When that is done it should be able to detect it automatically. Look on your other machine how it should look.
For the ssh problem you might need to clean and remake your /home/user/.ssh/known_hosts and id_dsa.pub
I use Ubuntu 9.10 & 9.04. When I plug my n900 into the USB port everything usually works fine but now and then won't connect again.
It seems like an intermittent problem and my only solution is to switch the n900 off and then plug it back in and then everything seems to work fine afterwards. When I have finished disconnect the n900 and then switch it back on.
Connects fine on my Lucid install with no messing. However, I do find that after using Easy Debian I cannot connect via USB Mass Storage mode until I reboot my N900.