Using my local site with latest Moodle 2.0 RC2, I created a wiki, created a few pages then tried the various map menu options. The links option gave the following error:

Coding error detected, it must be fixed by a programmer: PHP catchable fatal error

Debug info: Object of class stdClass could not be converted to string
Stack trace:

• line 333 of /lib/setuplib.php: coding_exception thrown
• line 1226 of /lib/weblib.php: call to default_error_handler()
• line 1592 of /mod/wiki/pagelib.php: call to format_string()
• line 1430 of /mod/wiki/pagelib.php: call to page_wiki_map->print_navigation_content()
• line 68 of /mod/wiki/map.php: call to page_wiki_map->print_content()