[ALUG] Warning: the ECDSA host key for '...' differs from the key for the IP address '...'

I have just received: Warning: the ECDSA host key for '...' differs from the key for the IP address '...' .. when trying to SSH to a web server I manage. I expect these kind of warnings if I've changed IPs, or reinstalled SSH, or reinstalled the OS, but I'm not aware of having done anything that could provoke this warning. Googling just gives me endless ways to fix the problem by removing the cached key, but I'm finding precious little advice on what to do if the warning has no obvious cause. Suggestions? -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) 21 Drakes Mews, Milton Keynes, MK8 0ER