i have the same problem in my ubuntu (upgraded 10.10 to 11.04).
when i connect with that => ssh A.B.X.X no problem.
but when i try connect to => ssh A.(B+1).X.X , i gets error that "Read from socket failed: Connection reset by peer"
then i install putty (apt-get install putty) when i use putty for ssh connections there is no problem.
i have the same problem in my ubuntu (upgraded 10.10 to 11.04).
when i connect with that => ssh A.B.X.X no problem.
but when i try connect to => ssh A.(B+1).X.X , i gets error that "Read from socket failed: Connection reset by peer"
then i install putty (apt-get install putty) when i use putty for ssh connections there is no problem.