Today my Keychain Access (in german Schlüsselbundverwaltung crashed reproducibly on startup. The first symptom was actually that Safari did not remember some passwords. Starting keychain access resulted in 100% reproducible crashes.
I found part of the solution on this german page:
Enable 'Start in 32-bit mode' on the Keychain Access program. This made it possible to start the Keychain Access and also the First Aid. The First Aid would however still crash and neither print a concrete problem nor repair it. It would just print 'crashed unexpectedly' (or so, in german).
iTunes would also still crash with the same error message (the same traceback) as Keychain Access.
So I rolled back the ~/Library/Keychains/login.keychain to a two weeks older version and this solved the problem. Apparently the keychain was corrupted. Now iTunes works again and I also can set Keychain Access back to 64 bit mode.
A bit frightening still.