We are having Game module problems, too. The problem coincides with our recent upgrade to Moodle 2.4 (20121203).
Students and teachers see the following, without debugging on:
Coding error detected, it must be fixed by a programmer: PAGE->yui2_lib() is not available any more, use YUI 2in3 instead, see MDL-34741 for more information.
More information about this error
With debugging on, we get the following stack trace:
Error code: codingerror
• line 319 of /lib/outputrequirementslib.php: coding_exception thrown
• line 61 of /mod/game/view.php: call to page_requirements_manager->yui2_lib()
We (by "we" I mean the real technicians whom I call when it is time for an update) have not applied the most recent Moodle 2.4+ update.
I have installed the 2012121201 updated Game module - Thanks for pointing out its availability, Rob - but the error and resulting stack trace are unchanged.
Any advice is greatly appreciated - the teachers really miss this module!