concurrent_vector returns invalid data

[zre]

using : VC++ 2013
concurrency::concurrent_vector<datanode*> dtnodelst

Occasionally when I do dtnodelst->at(i) .... I am getting an invalid address (0XCDCD.. ofc) which shouldn't be the case cause after I do push back, I never delete or remove any of the itms ( even if I delete it should have returned the deleted old address... but I am not ever deleting so that is not even the case )
dtnodelst itm = new dtnodelst ();
....
dtnodelst->push_back(itm);

any ideas on what might be happening ?

p.s. I am using windows thread pool. some times .. I can do 8million inserts and find mostly goes fine .... but sometimes even 200 inserts and finds will fail. I am kind of lost. any help would be awesomely appreciated!!

thanks and best regards