exe c++ boot at windows start but not working, run manually it works

[rv2010]

Hello,
I created a small application in C + + with Visual C++ 2010 Express. No error message.
- Started manually: everything is OK (it wrote a text in a txt file)
- To run this application at start of windows, I created a key regedit (HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows \ CurrentVersion \ Run), the program starts without problems (I see it in task manager) but it does not work, the text file is not written !!!!!
Where is the problem?
A parameter in the project properties in vc++?
Thank!

Here is the code:

#include <fstream>
#include <windows.h>

int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
static std:fstream g_log("log2.txt");
g_log << "message" << std::endl;
Sleep(INFINITE);
return 0;
}