ssh terminal window closes immediately when opened

I am seeing some odd behavior when using the Terminal app to open an ssh window to a remote machine. I normally connect to many different Linux servers from my MacBook Pro running Mac OS X 10.7.3, with Terminal 2.2.2 (303).

I have a list of the servers' IP addresses in the New Remote Connection window's ssh group. When I select one of the servers (10.x.y.120, for instance), enter a username, and click Connect, an ssh window opens and I can enter my password and get to work.

However, starting yesterday, for a couple of the machines (10.x.y.182 and 10.x.y.194), when I follow this procedure an ssh window opens and then immediately disappears. For other servers, the window opens as usual.

Here's the kicker: If I open a terminal window on my MacBook Pro itself, then run ssh on the command line to the machine that I can't reach through the New Remote Connection window, the connection works perfectly. It only fails when I do it through Terminal.

I have tried deleting the entry in New Remote Connection, and creating it again, but that didn't help. This is happening on a machine that was just restarted. One thing that did change was that I applied the latest Mac OS updates over the weekend. I don't remember which versions they were.

Things used to work last week, so something broke recently. Are there any logs I could look at for more information? Are there any configuration or data files that might have become corrupt? Thanks in advance for your help.

Here's what happened. On the machines I was trying to reach (10.x.y.182 and 10.x.y.194), in the time when I was not using them they had their hard disks replaced and the OS reinstalled. This gave them new SSH keys, invalidating the ones I had in my ~/.ssh/known_hosts file. Unfortunately, Terminal.app did not surface this problem to me.

By deleting the entries for those machines in ~/.ssh/known_hosts, I forced the system to pull down the new keys and ask me if I wanted to use them. With this done, connections worked perfectly as usual. Oddly, however, even before I changed ~/.ssh/known_hosts, connections using the DNS name of the machine (svr10 and svr20) worked. Weird.

Thanks, everyone, who looked at this problem.