Hi Chris,
I was having a similar issue with a global glossary that was added to the frontpage of my Moodle instance.
You are probably seeing an error similar to this on your php logging:
Default exception handler: Unsupported redirect detected, script execution terminated Debug: \nError code: redirecterrordetected\n* line 2527 of /lib/weblib.php: moodle_exception thrown\n* line 3151 of /lib/moodlelib.php: call to redirect()\n* line 3249 of /lib/moodlelib.php: call to require_login()\n* line 29 of /mod/glossary/showentry_ajax.php: call to require_course_login()\n, referer: http://example/course/view.php?id=5
To fix this I had to go to Site Administration --> Front page -->Front page settings --> change Default frontpage role from None to Guest or Student.
After that all the non administrators had rights to view the global glossary window throughout the site.