If you are running accross this error

  
1
2

  
[BUG] cross-thread violation of rb_gc()
ruby 1.8.6 (2008-08-11) [universal-darwin9.0]

- say you are are installing the latest so-called "stable" typo version on your OSX machine - then you might see the above error. Here is the solution: remove the bundled json gem!: It is version 1.1.3, which is way old, and apparently it contains some binaries that were compiled using ruby 1.8.6. Just install the "json" gem locally.