Using 'Library Organizer' to copy objects from the 'GeoWorkspace contents' pane to the 'Library contents' pane results in the error message "This key is already associated with an element of this collection".
Review the list of objects displayed in the 'GeoWorkspace contents' pane to determine if there are any duplicate object names.
For instance in older versions of GeoMedia it may have been possible to create duplicate folder names within the Styles system resulting in two folders with the same name (such as Railroads and Railroads) at the same location in the Styles list. Duplicate object names could potentially exist for other object types as well, so if you don't find a duplicate object name within the Styles list, check the other categories within the 'GeoWorkspace contents' pane (e.g. Queues, Legends, etc).
If you find any duplicate object names within any of the 'GeoWorkspace contents' categories, close the Library Organizer dialog. Then go to the command used to manage the object type where the duplicate object was identified. For instance if you found a duplicate folder name within the Styles folder you would select the Styles command. Then on the Styles dialog, find the duplicate folder names and rename one fo them so that the name of the two folders are different. For instance if there were two folders named 'Railroads' as noted in the example above, you can rename one of the folders to 'Railroads2'.
Once all of the duplicate objects are resolved (by either renaming or deleting the duplicate), reopen the Library Organizer command and try to copy objects from the 'GeoWorkspace contents' pane to to the 'Library contents' pane again.