[AUCTeX] Emacs problem compiling ConTeXt documents

[Manuel González Suárez]

Hello everyone.
I am sending this message because I'm desperate. I have already sent another, but can not solve the problem. I have installed the latest version of Emacs, Ruby 200 and TeXLive 2013 under Windows (XP and Vista). I can compose and compile LaTeX documents in Emacs perfectly, but when it comes ConTeXt format documents, Emacs gives me the following error:
ERROR: invalid multibyte escape: / \ xFF / (SyntaxError)

--- TeX said ---
C :/ Ruby200/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb: 45: in `require ': C :/ texlive/2012/texmf-dist/scripts/context/ruby/base/switch.rb : 501: invalid multibyte escape: / \ xFF / (SyntaxError)
--- HELP ---
No help available

I've already tried several options and I have included the path to the folder where I have Emacs and Ruby, but I can not make compile.
Thank you for your attention.
Manuel Gonzalez.