The current version of RubyGems library (0.8.10) doesn't alter the 
LOADPATH. Instead it overrides Kernel#require with something like this:

module Kernel
  alias require__ require

  def require(path)
    require__ path
  rescue LoadError => load_error
    ... tries to require a gem ...
  end
end

So, it will always try to get stuff from LOADPATH first, only then go to 
RubyGems.

Earlier versions used to change LOADPATH, indeed. So, the answer to your 
question _may_ be as simple as "upgrade RubyGems"

Alex