线程故障！！

void CMFC_Ant_MultithredingDlg::OnAnt() //启动线程！！！
{
// TODO: Add your control notification handler code here
    //m_Param->m_Paint=this;
AfxBeginThread(ThreadFun,(LPVOID)this);
}UINT CMFC_Ant_MultithredingDlg::ThreadFun(LPVOID pParam)
{   
srand( (unsigned)time( NULL ) );
CMFC_Ant_MultithredingDlg *m_Param=(CMFC_Ant_MultithredingDlg*)pParam; 
CClientDC dc(m_Param);
int m_direction;
m_Param->m_Param->m_Ant.x=200;
m_Param->m_Param->m_Ant.y=200;
dc.SetPixel(m_Param->m_Param->m_Ant.x,m_Param->m_Param->m_Ant.y,RGB(255,0,0));
for (int i;i<1000;i++)
{
m_direction=rand()%8;
switch(m_direction)
{
case 0:
dc.SetPixel(m_Param->m_Param->m_Ant.x--,m_Param->m_Param->m_Ant.y++,RGB(255,255,255));
break;
case 1:
dc.SetPixel(m_Param->m_Param->m_Ant.x,m_Param->m_Param->m_Ant.y++,RGB(255,255,255));
break;
case 2:
dc.SetPixel(m_Param->m_Param->m_Ant.x++,m_Param->m_Param->m_Ant.y++,RGB(255,255,255));
break;
case 3:
dc.SetPixel(m_Param->m_Param->m_Ant.x--,m_Param->m_Param->m_Ant.y,RGB(255,255,255));
break;
case 4:
dc.SetPixel(m_Param->m_Param->m_Ant.x++,m_Param->m_Param->m_Ant.y,RGB(255,255,255));
break;
case 5:
dc.SetPixel(m_Param->m_Param->m_Ant.x--,m_Param->m_Param->m_Ant.y--,RGB(255,255,255));
break;
case 6:
dc.SetPixel(m_Param->m_Param->m_Ant.x,m_Param->m_Param->m_Ant.y--,RGB(255,255,255));
break;
case 7:
dc.SetPixel(m_Param->m_Param->m_Ant.x++,m_Param->m_Param->m_Ant.y--,RGB(255,255,255));
break;
}
dc.SetPixel(m_Param->m_Param->m_Ant.x,m_Param->m_Param->m_Ant.y,RGB(255,0,0));
//Sleep(1);

}
return 1;
}调试通过了！但是点按扭就出错误！！！为什么啊？
没分了！不然一定多给！谢谢！！