Problem integrating Forum into Page

I would like to have the Forum node displayed together with a custom block which introduces the forum and gives instructions to new users.
I am using the Page Manager
If I try to add an existing node in the 'Content' stage, and enter 'forum' (with or without a preceding backslash) into the 'Enter the title or NID of the Node' edit box I get the error message 'invalid node'

If I try to add 'Active Forum Topics' from the list of activities I get a number of warnings: 'Attempt to assign property of non-object' in ctools_block_content_type_render() on lines 152, 153, 162 and 166 of ..sites/all/modules/ctools/plugins/content_types/block/block.inc,
and in ctools_content_render() on lines 289 and 293 of ../sites/all/modules/ctools/includes/content.inc

Am I doing something wrong somewhere, is there a module missing, or have I found a bug?
I have Drupal 7.13 and Chaos Tool Suite 7.x 1.2 with all elements apart from Chaos tools AJAX example and Chaos tools Plugin example enabled.
Can anybody help please?