c++0x compiles but eclipse editor errors even with -gnu++0x discovery

I use some code to report duration of a task using std::chrono::high_resolution_clock ... part of c++0x.

I can successfully compile c++0x features in eclipse cdt using the -gnu++0x flag. Although successfully compiling, the editor seemed unaware of c++0x i.e. it displayed errors for any c++0x features in my code. I solved that by adding the -gnu++0x flag to my project discovery options. Note: doesn't show fixed until you do another compile and rebuild the index ...

-E -P -v -dD "${plugin_state_location}/specs.cpp" -std=gnu++0x

I still have one last editor error that I can't rid myself of "Symbol 'duration_cast' could not be resolved" (I had a pic but new users can't post pics)

Anyone have any ideas on how to fix this? Here is the code:

#ifndef _scoped_timer_h_
#define _scoped_timer_h_

#include <iostream>
#include <chrono>
#include "boost/noncopyable.hpp"
#include "boost/format.hpp"

using namespace std::chrono;

  // Utility class for timing and logging rates
// (ie "things-per-second").
// NB _any_ destructor invokation (including early return
// from a function or exception throw) will trigger an
// output which will assume that whatever is being measured
// has completed successfully and fully.
class scoped_timer : boost::noncopyable
{
public:


  scoped_timer(
    const std::string& what,
    const std::string& units,
    double n
  )
    :_what(what)
    ,_units(units)
    ,_how_many(n)
    ,_start(high_resolution_clock::now())
  {}

  ~scoped_timer() {
    high_resolution_clock::time_point stop = high_resolution_clock::now();
    const double t = 1e-9 * duration_cast<nanoseconds>(stop-_start).count();
    std::cout << (
      boost::format(
        "%1%: %|2$-5.3g| %|3$|/s (%|4$-5.3g|s)"
      ) % _what % (_how_many/t) % _units % t
    ) << std::endl;
  }

private:

  const std::string _what;
  const std::string _units;
  const double _how_