线程函数中的某段代码，总是抛出异常，不解？

CString strNewData,strOldData;
CString strNewData2,strOldData2;

try
{
strNewData.Format(“%g”, pMain->m_CPRKManager.m_chPRKRecogBuffer2[pMain->m_CSysConfigInfo.m_ulDCCheck1]);
if( strNewData != strOldData)
{
++m_gdDataChange1Counter;
strOldData = strNewData;
}
//检测点2.2015.06.25
strNewData2.Format(“%g”, pMain->m_CPRKManager.m_chPRKRecogBuffer2[pMain->m_CSysConfigInfo.m_ulDCCheck2]);
if( strNewData2 != strOldData2)
{
++m_gdDataChange2Counter;
strOldData2 = strNewData2;
}
}
catch(…)
{
//要是线程函数每秒执行一次的话，一天大约有个5次左右。
}