Memory Leak

I''m using D3D8 to load several mesh objects along with their materials and all are put in the managed resource pool. I''m tracking the memory usage with the task manager. The problem is that when I release all my objects, the task manager doesn''t show any decrease in the memory usage. When I''m reloading the same objects again (without quiting the application), the memory usage grows even further and so on. Is there anything to put into consideration when dealing with managed resources? Is there any way to make sure that a COM object is not being released? Thanks in advance.