Our suite would sometimes randomly hang when running a certain spec, but we weren't able to tell which one. With the below RSpec around filter you can see the spec that is currently running by inspecting the process name.
$ rspec spec_spec.rb &
[2] 64968
$ ps | grep rspec
64968 ttys005 0:00.24 rspec /Users/miha/spec_spec.rb:10 "Dummy spec waits for 100 seconds"