I just bumped across this bug again with a dell mini. It affected all ssh connections, even those on my local wlan. This machine has had all the updates applied that are available from deb http://dell-mini.archive.canonical.com/ubuntu/ hardy-updates
Adding this to the end of /etc/network/if-pre-up.d/wireless-tools does workaround the issue for me after a reboot:
#fix for ssh to remote hosts hanging -- tlunde
/sbin/iwpriv eth1 set_vlanmode 0
I don't know how "sticky" the solution is (re: Tim's comment of 2008-09-25)
Should we consider the dell-mini hardy-updates abandoned and change /etc/apt/sources.list ?