[allr]

More importantly, FFI 1.9.1 was released today (http://rubygems.org/gems/ffi) and completely broke knife-solo, returning a huge stack trace ending with:

You may have encountered a bug in the Ruby interpreter or extension libraries.

reverting back to FFI 1.9.0 did the trick.

[xentronium]

1.9.1 is yanked as of now, which means no one can install it accidentally.