Ошибка приведения типа из shared_ptr

У меня есть следующий код:

namespace {
class CatBondEvent
{
public:
CatBondEvent(Date date) : date(date){}
virtual ~CatBondEvent(){}
Date date;

bool operator< (CatBondEvent &other) { return date<other.date;}
};

class CatEvent : CatBondEvent
{
public:
Real loss;
CatEvent(Date date, Real loss) : CatBondEvent(date), loss(loss) {}
};

class CollateralCoupon : CatBondEvent
{
public:
Real unitAmount;
CollateralCoupon(Date date, Real unitAmount) : CatBondEvent(date), unitAmount(unitAmount) {}
};

class CatBondCoupon : CatBondEvent
{
public:
CatBondCoupon(Date date) : CatBondEvent(date) {}
};

void fillEvents(std::vector<boost::shared_ptr<CatBondEvent> > &events,
Date startDate,
Date endDate,
boost::shared_ptr<std::vector<std::pair<Date, Real> > > catastrophes,
boost::shared_ptr<Bond> collateral,
boost::shared_ptr<std::vector<Date> > couponDates)
{
for(int i=0; i<catastrophes->size(); ++i)
{
events.push_back(boost::shared_ptr<CatBondEvent>(new CatEvent((*catastrophes)[i].first, (*catastrophes)[i].second)));
}
const Leg& cashflows = collateral->cashflows();
for(int i=0; i<cashflows.size() && cashflows[i]->date()<=endDate; ++i)
{
boost::shared_ptr<CashFlow> cashflow = cashflows[i];
if(cashflow->date() >= startDate)
{
events.push_back(boost::shared_ptr<CatBondEvent>(new CollateralCoupon(cashflow->date(), cashflow->amount())));
}
}
for(int i=0; i<couponDates->size(); ++i)
{
Date couponDate = (*couponDates)[i];
if(couponDate >= startDate)
{
events.push_back(boost::shared_ptr<CatBondEvent>(new CatBondCoupon(couponDate)));
}
}
}
}

И я получаю следующие ошибки компиляции:

Error   37  error C2243: 'type cast' : conversion from '`anonymous-namespace'::CollateralCoupon *' to '`anonymous-namespace'::CatBondEvent *' exists, but is inaccessible   c:\boost\boost_1_49_0\boost\smart_ptr\shared_ptr.hpp    184
Error   36  error C2243: 'type cast' : conversion from '`anonymous-namespace'::CatEvent *' to '`anonymous-namespace'::CatBondEvent *' exists, but is inaccessible   c:\boost\boost_1_49_0\boost\smart_ptr\shared_ptr.hpp    184
Error   38  error C2243: 'type cast' : conversion from '`anonymous-namespace'::CatBondCoupon *' to '`anonymous-namespace'::CatBondEvent *' exists, but is inaccessible  c:\boost\boost_1_49_0\boost\smart_ptr\shared_ptr.hpp    184

Есть идеи, что пошло не так и как это исправить?