Samsung 300k Tool Error 995

My serial app runs good in my pc but occtially gives an error Reading or Writing to port. GetLastError() returns with 995, which states the following (from MSDN):
995 ERROR_OPERATION_ABORTED The I/O operation has been aborted because of either a thread exit or an application request. I am using two separate threads for read and write, but they don't exit when I get this error.
Did anybody ever get this error? I am using Overlapped mode communication with Win2000.
BOOL CSerialPort::WriteBuffer(char *lpBuf, DWORD dwToWrite)
{
OVERLAPPED osWrite = {0};
DWORD dwWritten;
DWORD dwRes;
BOOL fRes;
DWORD lrc = 0;
// Create this write operation's OVERLAPPED structure's hEvent.
osWrite.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (osWrite.hEvent NULL)
{
// error creating overlapped event handle
AfxMessageBox('Error creating Overlapped event');
return FALSE;
}
// Issue write.
if (!WriteFile(m_hComm, lpBuf, dwToWrite, &dwWritten, &osWrite))
{
lrc = GetLastError();
if (lrc != ERROR_IO_PENDING)
{
// WriteFile failed, but isn't delayed. Report error and abort.
char err_code[3];
sprintf(err_code,'%i',lrc);
AfxMessageBox('WriteFile failed: Error Code = '+ (CString) err_code);
fRes = FALSE;
}
else
{
// Write is pending.
dwRes = WaitForSingleObject(osWrite.hEvent, INFINITE);
//AfxMessageBox('Write is pending');
}
switch(dwRes)
{
// OVERLAPPED structure's event has been signaled.
// AfxMessageBox('Overlapped's structure's even has been signaled'); // not here
case WAIT_OBJECT_0:
if (!GetOverlappedResult(m_hComm, &osWrite, &dwWritten, FALSE))
fRes = FALSE;
else
{
// Write operation completed successfully.
//AfxMessageBox('Write operation completed successfully');
fRes = TRUE;
}
break;
default:
// An error has occurred in WaitForSingleObject.
// This usually indicates a problem with the
// OVERLAPPED structure's event handle.
fRes = FALSE;
break;
}
}
else
// WriteFile completed immediately.
fRes = TRUE;
CloseHandle(osWrite.hEvent);
return fRes;
}