As of version 6.03, Hippo CMS support configuration of the maxobjects of the MRUMemory store used in the TreeGenerator. The TreeGenerator generates the folder tree of documents and assets in the cms. It has a EventAwareTransientStore, which implements MRUMemoryStore. By default, the MRUMemory store maxobjects is set to 100. Since the TreeGenerator stores every folder as a distinct key, one single user quickly uses 100 cachekey objects. Hence, when having multiple users and multiple repository namespaces running under one single cms, this maxobjects of 100 is way to low. Thorough testing has not yet been done, but default configuring of 500 maxobjects in the cms when running one namespace is adviced. When running multiple namespaces with one cms, increase the number of maxobjects. At the moment, no estimates about the maximum value are available. In project.properties or build.properties you can set the maxobjects as:

cms.eventaware-store.maxobjects=500