IMallocSpy crashing my computer

I try to register an implmentation of the IMallocSpy but each time a  malloc  (:IMalloc, created with CoGetMalloc) is called it enters the PreAlloc but when it finishes the procedure itcomes up with the well known "Access violation error ..."
I suspect that the problem is arround the way I implement my IMallocSpy : Since I cannot specify the parent interface of my custom MallocSpy (I called it ICMallocSpy) to be IMAllocSpy ( I could not found it in the available interfaces: doesnt have a type lib )   I tryed to get arround into 2 ways : one I created a new com object and I changed in the source code the ICMallocSpy = interface (IUnknown) to be : ICMallocSpy=interface (IMallocSpy) ... same acc. violt. err.
second try : I created a new COM obj, that was implementing an inteface called :IWhatever and the object was implementing actually the IMallocSpy , not the IWhatever : TWhatever=class(TTypedComObject,IWhatever,IMallocSpy)
   ...same problems
Could please anyone help me out with this one?