std::vector push_back() function throwing access violation

I'm getting access violation error when I try to insert into vector. This is what I have, I'm getting access violation error when it tries to push_back() in the _Inside(..) function of vector.:

iPathSolver* getPathSolver(iPathnode* Location, iNode* actor)
        {
            PathSolver* s = new PathSolver(Location, actor);
            solvers.push_back(s);
            return (iPathSolver*)solvers.back();
        }

class PathSolver : public iPathSolver
    {
    private:
        iNode* actor;
        Vector<float, 3> old_loc; //this is another class created by me..
        iPathnode* next_loc;
        std::vector<iPathnode*> pathChildren; //ArrayList is std::vector
        iPathnode* current_Loc = nullptr; //3-4 iPathnodes 
        std::map<int, iPathnode*> openList; //3-4 maps

    public:
    PathSolver::PathSolver(iPathnode* Location, iNode* act)
        {
            current_Loc = Location;
            destination = nullptr;
            actor = act;
            old_loc = current_Loc->getPosition();
            next_loc = current_Loc;
        }
   //etc....
}