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Log in as root, type 'lsof /dev/ttyx' where the 'x' in /dev/ttyx is the terminal number of the hung virtual console. This will show you the process that occupies this tty. Kill it and the getty process for that virtual console should respawn.
That's all for now. We will keep you all posted as and when we find some more good tips to add to this list. By the way, do mail us your tips and we will include them in here.
I was able to kill a dead ssh session that was there for like three weeks.
Obviously you don't have to login as root. You only need to be root if the process to be killed belongs to someone else.