IMO, it is nothing to worry about, when you updated the firmware you ssh keys changed and since old ssh keys get stored on your host machine under ~/.ssh/known_hosts, it sees a conflict and gave this warning. You can rectify this by deleting old keys, open file ~/.ssh/known_hosts with a suitable editor like vim or nano and delete the line containing old keys and try ssh again.
Posts made by Ayan Pahwa
RE: Omega 2+ suddenly burnout!!!