If you installed Security Update 002 for leopard and suddenly ssh tells you “bus error”, the answer lies here:
Apparently the guys at rogue amoeba have some work to do – we need instant hijack!
If you are too lazy to read that thread, the fix is:
sudo /usr/local/hermes/bin/hermesctl unload
thereby uninstalling instant hijack and fixing the problem. Somehow…
… and here’s the fix from Rogue Amoeba: