I brought this on myself, so I don't believe it is an error that should be reported as an issue under OG module, but hopefully I can get some help here.
Synopsis
Group Visibility Settings in Group Details Block in Blocks Module reads "No group types have been defined. Please define at least one group node type under administer >> settings >> og"
Group home page node type is set to "group" in Organic Group Configuration settings.
Background
I installed OG and associated modules and began to notice wierd behavior in OG_Galleries. After extended discussion with the author of OG_Galleries (http://drupal.org/node/83179) it appeared that my condition could not be replicated in a normal operating environment.
I created a sandbox installation (Install B), using same modules activating only core, OG modules and other required modules (Views, etc). The Sandbox worked perfectly. I next deactivated all non-OG modules in the other installation (Install A) and the problem persisted there. I confirmed all admin settings were identical yet problem continued.
I deactivated all OG modules in Install A, deleted module folders, dropped OG tables and reinstalled OG from the ground up including downloading all new tars for OG and repatching as had been necessary in the past. That probably wasn't too smart an idea, as I wound up with a really broken OG. I traced the problem to the fact that the reinstalled OG did not recreate the tables that I had dropped. Fortunately I discovered the Devel module and re-installed all of the OG modules using the reinstallation feature of Devel.