vector::clear() method throw error "vector erase iterator outside range" in C++ VS2010

In my VS2010 project, there is a part of the code like:

LRESULT CDlgTrackTime::OnMsgBeginSearch( WPARAM wParam, LPARAM lParam )
{
        m_vtFileDay.clear();
        m_PlayList.clear();
        ...
}

where m_vtFileDay is defined as follows:

typedef struct _tagAVFILEDay_S
{
    int nYear;
    int nMonth;
    int nDay;
    char szFolder[MAX_PATH];            
}AVFILEDay_S, *LPAVFILEDay_S;
typedef std::vector< AVFILEDay_S >      VecFileDay;

When m_vtFileDay.clear() runs, in vector file as follows:

#if _ITERATOR_DEBUG_LEVEL == 2
        if (_Last < _First || _VICONT(_First) != this
            || _VIPTR(_First) < this->_Myfirst
            || this->_Mylast < _VIPTR(_Last))
            _DEBUG_ERROR("vector erase iterator outside range");
        pointer _Ptr = _Move(_VIPTR(_Last), this->_Mylast,
            _VIPTR(_First));
        _Orphan_range(_VIPTR(_First), this->_Mylast);
#else
...

VS returns "vector erase iterator outside range" as the debug error message at _ITERATOR_DEBUG_LEVEL == 2. The local variable at that function level shows that both _Last and _Last_arg points to 0x00000000 while _First_arg and _First are still a valid pointer pointing to a AVFILEDay_S.

My question is how I could resolve this problem? Is this a memory leak because szFolder[MAX_PATH] is not properly deleted? Or should I just set _ITERATOR_DEBUG_LEVEL == 1? Thank you so much!