So I've been having problems with encodings after upgrading from JRuby 1.7.6 (I think the next version I tried after that was 1.7.8, but surely 1.7.11).

Reproduce in 1.7.18:

require 'nokogiri'
require 'open-uri'

Nokogiri::HTML(open("https://www.youtube.com/results?search_query=bears+in+exile+guppy+gmma+indicator+part+2")).to_html

.rvm/gems/jruby-1.7.18/gems/nokogiri-1.6.5-java/lib/nokogiri/xml/node.rb:834:in `native_write_to':
""\xC4\x8D"" from UTF-8 to US-ASCII (Encoding::UndefinedConversionError)

It works fine with 1.7.6 (also works on MRI 2.1.2). I'm not sure if 1.7.11 had the exact same issue, I just know that I had issues with encodings.
Note: .to_html is crucial to trigger the error.