Memory Leak in C++ STL library - Visual Studio 2005

There's something wrong with the ios_base class in Visual Studio 2005. I was debugging my program and I noticed a memory leak. Since I could not understand what was causing that leak, I've tried using a memory leak detection tool (Rational Purify) and I found that the ios_base class causes a memory leak.

I just tried to write this piece of code

#include <sstream>

int main(void)
{
    std::stringstream myStream;
    //nothing else
   return 0;
}

The memory leak detection program tells me that:
--Memory leak of 4 bytes from 1 block allocated in
--std::basic_iostream<char,char_traits<char>::std>::basic_iostream<char,char_traits<char>::std>(basic_streambuf<char,char_traits<char>::std>::std*)
--at file         xiosbase
--at method    std::ios_base::_Init(void)
--at line    _Ploc = _NEW_CRT locale;

Is this true or I am misinterpreting the program's output?

Please help me!

Thanks