uhhh... no idea what you're talking about.
I'm Oedipus in the technical woods. Not only am I a babe. My ankles are nailed together.
A lot of this is made worse by Apple's misguided attempts to make the system 'more friendly'.
Anyway, I don't have proper access to a mac right now, but I think it's this:
1. In finder, go to Applications -> Utilities -> Terminal
2. This should give you the command prompt.
3. Enter the following command
exactly - cut-and-paste is probably best:
rm ~/.ssh/known_hosts
4. If fugu is running, shut it down.
5. Launch fugu, try to connect
Let us know if that works, or what happens if it doesn't...