Well, I tried deactivating Custom Press which is a plugin for creating custom fields, taxonomies and post types and then I was able to activate Collabpress. However, now when I go to one of my sites and activate Custom Press again, I get this message on the settings page for THAT plugin:
Rendering of admin template /home4/maubenco/public_html/wp-content/plugins/collabpress/ui-admin/navigation.php failed
These two just seem to conflict. I may just end up setting up collabpress on one of my subsites that isn't using custom press. Do you have any suggestions on how to make these work together? Thanks a lot for your prompt responses.