But Darren’s comment about rm-ing his known_hosts got me thinking about how you could get round that. I put up a longer writeup on my site but the long and short of it is in Bash you can say
(x=3; head -n$(($x-1)) known_hosts; tail -n$((`wc -l known_hosts | cut -d ' ' -f 1`-$x)) known_hosts) > t2 && cat t2 > known_hosts where x is the offending line number of the key (the warning tells you which line in the file to remove).

My preferred way is less typing heavy and more perlish perl -nle 'print if(++$i!=3)' known_hosts > t2 && mv t2 known_hosts would do it

Thanks …!