help! crash on UIQ3

Thanks for your reply.
My code like following:
class CHttpClient : public CBase, public MHTTPDataSupplier, public MTimeOutNotifier, MUserCancelNotifier,public MHTTPAuthenticationCallback
{
....
private:
RHTTPSession iSess;
....
};

void CHttpClient::ConstructL(const TDesC& aSource, const TDesC& aFilename)
{
iUtils = CHttpClientUtils::NewL(KHttpExampleClientTestName);

// Open the RHTTPSession
iSess.OpenL();

// Install this class as the callback for authentication requests
InstallAuthenticationL(iSess);

User::LeaveIfError(iFileServ.Connect());

// Start a timer
iTimer = CTimeOutTimer::NewL(EPriorityHigh, *this);

iCancelHandle = CUserCancel::NewL(EPriorityHigh, *this);
UserCancelSet_t ucs;
ucs.handle = TM_AU_HTTP_User_Cancel;
ucs.status = &(iCancelHandle->iStatus);
if(!DoCallback(iDownloaderCfg->tls(), Tmu_SET_USER_CANCEL_HANDLE, (TAny* )&ucs))
{
User::Leave(TM_CHTTPCLIENT_USER_CANCEL);
}
iTransObs = CHttpEventHandler::NewL(*iUtils, iTimer, iDownloaderCfg);
iSource.Copy(aSource);
iTransObs->SetFileName(aFilename);
}

There is no return value for RHTTPSession::OpenL(). It crashes before return. Do you have any way to get last error?
Thanks.