Hi Arlene,
I am using Namemapping without any problem for a complex dynamic web application when the contents of the mapped object (i.e. the object itself and its children) can be changed very significantly or even be recreated.
May it be that the problem is not with 'caching' but with the way how tested objects are namemapped and/or how they are used by the test code.
If you provide us with more specific details instead of generic "object property changes are giving us a lot of trouble..." there is a chance that somebody will have some good idea that might help.