Why does std::sort() without prefix "std" not compile in Visual Studio 2010 when using a lambda?

Question

I have encountered a situation where a call to std::sort() works without explicitly writing the namespace. According to Using std::sort() without prefix "std" and also without "using namespace std;" compiles successfully, the compiler uses ADL and considers the namespaces of the arguments. Since vector is in std, it finds std::sort.

In the following program, ADL fails for the second call to sort when using Visual Studio 2010. Since the iterators are the same, std::sort should be findable. But the compiler says C3861 'identifier': identifier not found. Why?

#include <algorithm>
#include <vector>

class StableSortClass
{
public:
  int m_i;
};

bool lessStableSortClass(const StableSortClass & lhs, const StableSortClass & rhs) {return lhs.m_i < rhs.m_i;}

int main(int argc, char **argv)
{
  std::vector<StableSortClass> vec;

  // works because of ADL without std::
  sort(vec.begin(), vec.end(), lessStableSortClass);
  
  // does not compile in Visual Studio 2010
  sort(vec.begin(), vec.end(), [](const StableSortClass & lhs, const StableSortClass & rhs) {return lhs.m_i < rhs.m_i;});

  // compiles
  std::sort(vec.begin(), vec.end(), [](const StableSortClass & lhs, const StableSortClass & rhs) {return lhs.m_i < rhs.m_i;});

  return 0;
}

EDIT

To answer the comments so far:

1. I don't want to rely on ADL. I found code in a header and wondered why the compiler does not complain to the missing std::. I then noticed that the std:: is sometimes required and sometimes not, hence this question.
2. C3861 'identifier': identifier not found is the complete error message the compiler gave to me. Nothing more.
3. Yes, some folks do maintenance for old production systems where VS2010 is used. It could be worse ;-)