pygments.rb: MentosError header errors

1.9.3p286 :001 > require "pygments"
 => true 
1.9.3p286 :002 > Pygments.highlight("foo")
MentosError: Failed to get header.
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:351:in `rescue in get_header'
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:332:in `get_header'
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:229:in `block in mentos'
    from /home/adam/.rvm/rubies/ruby-1.9.3-p286/lib/ruby/1.9.1/timeout.rb:68:in `timeout'
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:203:in `mentos'
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:186:in `highlight'
    from (irb):2
    from /home/adam/.rvm/rubies/ruby-1.9.3-p286/bin/irb:16:in `<main>'

As far as I can tell, this is happening on a clean gem environment.

Curiously, installing python-pygments and calling Pygmentize.start("pygmentize") first gives, for one single subsequent call to highlight a slightly different message:

1.9.3p286 :003 > Pygments.start("pygmentize"); Pygments.highlight("foo")
MentosError: No header received back.
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:295:in `handle_header_and_return'
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:232:in `block in mentos'
    from /home/adam/.rvm/rubies/ruby-1.9.3-p286/lib/ruby/1.9.1/timeout.rb:68:in `timeout'
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:203:in `mentos'
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:186:in `highlight'
    from (irb):3
    from /home/adam/.rvm/rubies/ruby-1.9.3-p286/bin/irb:16:in `<main>'

1.9.3p286 :004 > Pygments.highlight("foo")
MentosError: Failed to get header.
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:351:in `rescue in get_header'
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:332:in `get_header'
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:229:in `block in mentos'
    from /home/adam/.rvm/rubies/ruby-1.9.3-p286/lib/ruby/1.9.1/timeout.rb:68:in `timeout'
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:203:in `mentos'
    from /home/adam/.rvm/gems/ruby-1.9.3-p286/gems/pygments.rb-0.3.2/lib/pygments/popen.rb:186:in `highlight'
    from (irb):4
    from /home/adam/.rvm/rubies/ruby-1.9.3-p286/bin/irb:16:in `<main>'