[Zope-dev] _getProductRegistryData('zclasses') returns non-existent Products -- permission to muck around?

My ProductRegistry has references to products which no longer exist in my Zope installation. This causes a variety of problems in lots of different places when other products try to get more information about all the products in the ProductRegistry (obviously). 1) How does this occur? 2) Is it OK to put my boots on, get in there and manually delete entries which refer to non-existent Products? TIA Ziniti