"A. The possible reasons for getting this error are:
* You have re-installed you system and trying to ssh to the newly installed system.
* You have assigned the IP address of one system to another system and trying to ssh.
* You system is dual boot with different ssh keys in both flavors of linux.
* You are using an IP for load balancing and trying to ssh to the same IP.
* You generated new ssh keys for your system. (Read this article for the re-generation of the host keys: Generate SSH host keys)
* Someone trying to do some nasty things"
