While trying to see the new blocks in action (and how all those block_instances and block_positions are used). I've ended with this problem:
1) create empty course
2) in course page, add "tags" block and add some tags.
3) create one forum and in forum page add the "tags" block again. Add some other tags (different in my case).
4) FIRST PROBLEM: Each time you add one tag in forum page, you're redirected to course page.
5) In course page, configure the block. It works without problem
6) In forum page, configure the block. SECOND PROBLEM. I get (nine times):
Incorrect context specified
line 474 of /lib/accesslib.php: call to debugging()
line 3075 of /lib/navigationlib.php: call to has_capability()
line 2513 of /lib/navigationlib.php: call to settings_navigation->load_module_settings()
line 546 of /lib/pagelib.php: call to settings_navigation->initialise()
line 561 of /lib/pagelib.php: call to moodle_page->magic_get_settingsnav()
line 122 of /blocks/settings_navigation_tree/block_settings_navigation_tree.php: call to moodle_page->__get()
line 847 of /blocks/moodleblock.class.php: call to block_settings_navigation_tree->get_content()
line 367 of /blocks/moodleblock.class.php: call to block_tree->formatted_contents()
line 801 of /lib/blocklib.php: call to block_base->get_content_for_output()
line 853 of /lib/blocklib.php: call to block_manager->create_block_contents()
line 315 of /lib/blocklib.php: call to block_manager->ensure_content_created()
line 6 of /theme/base/layout/general.php: call to block_manager->region_has_content()
line 607 of /lib/outputrenderers.php: call to include()
line 565 of /lib/outputrenderers.php: call to core_renderer->render_page_layout()
line 1173 of /lib/blocklib.php: call to core_renderer->header()
line 946 of /lib/blocklib.php: call to block_manager->process_url_edit()
line 1048 of /lib/pagelib.php: call to block_manager->process_url_actions()
line 649 of /lib/pagelib.php: call to moodle_page->starting_output()
line 560 of /lib/outputrenderers.php: call to moodle_page->set_state()
line 104 of /mod/forum/view.php: call to core_renderer->header()
(at the end... the configuration form is showed, and seems to be working)
Also, slightly offtopic, I've got some problems trying to imagine the meaning of the "parentcontexid" in block_instances tables (it's the context where the block "belongs to"). And also the "contextid" in block_positions (it's the context where the "configuration" belongs to. Doc pages doesn't look perfect IMO ( http://docs.moodle.org/en/Development:Very_flexible_block_system_proposal ). And I don't want to imagine how the hell I'm going to store all those inter-context relations, grrr in backup and restore (that's another problem).