For some of our instructors when they click on the maxamize and minimize (+, o, -) at the top of the gradebook categories (grader view) they receive a coding error:

Coding error detected, it must be fixed by a programmer: Invalid value in set_user_preference() call, value is is too long for the value column More information about this error

This error shows in the logs as:

[Thu Oct 10 20:10:28 2013] [error] [client 173.166.96.121] Default exception handler: A required parameter (attempt) was missing Debug: \nError code: missingparam\n* line 476 of /lib/setuplib.php: moodle_exception thrown\n* line 532 of /lib/moodlelib.php: call to print_error()\n* line 40 of /mod/quiz/processattempt.php: call to required_param()\n
[Thu Oct 10 20:14:24 2013] [error] [client 75.130.89.22] Default exception handler: Coding error detected, it must be fixed by a programmer: Invalid value in set_user_preference() call, value is is too long for the value column Debug: \nError code: codingerror\n* line 1789 of /lib/moodlelib.php: coding_exception thrown\n* line 1636 of /grade/report/grader/lib.php: call to set_user_preference()\n* line 110 of /grade/report/grader/index.php: call to grade_report_grader::do_process_action()\n, referer: http://pcilms.mportfolios.net/grade/report/grader/index.php?id=291&target=c1153&sesskey=TF6Dt0Lx1M&action=switch_minus
root@offsite:/var/log/apache2#

Also:
Thu Oct 10 20:22:25 2013] [error] [client 75.130.89.22] Default exception handler: Coding error detected, it must be fixed by a programmer: Invalid value in set_user_preference() call, value is is too long for the value column Debug: \nError code: codingerror\n* line 1789 of /lib/moodlelib.php: coding_exception thrown\n* line 1636 of /grade/report/grader/lib.php: call to set_user_preference()\n* line 110 of /grade/report/grader/index.php: call to grade_report_grader::do_process_action()\n, referer: http://pcilms.mportfolios.net/grade/report/grader/index.php?id=291
[Thu Oct 10 20:23:06 2013] [error] [client 75.130.89.22] Default exception handler: Coding error detected, it must be fixed by a programmer: Invalid value in set_user_preference() call, value is is too long for the value column Debug: \nError code: codingerror\n* line 1789 of /lib/moodlelib.php: coding_exception thrown\n* line 1636 of /grade/report/grader/lib.php: call to set_user_preference()\n* line 110 of /grade/report/grader/index.php: call to grade_report_grader::do_process_action()\n, referer: http://pcilms.mportfolios.net/grade/report/grader/index.php?id=291
[Thu Oct 10 20:23:18 2013] [error] [client 75.130.89.22] Default exception handler: Coding error detected, it must be fixed by a programmer: Invalid value in set_user_preference() call, value is is too long for the value column Debug: \nError code: codingerror\n* line 1789 of /lib/moodlelib.php: coding_exception thrown\n* line 1636 of /grade/report/grader/lib.php: call to set_user_preference()\n* line 110 of /grade/report/grader/index.php: call to grade_report_grader::do_process_action()\n, referer: http://pcilms.mportfolios.net/grade/report/grader/index.php?id=291
[Thu Oct 10 20:23:28 2013] [error] [client 75.130.89.22] Default exception handler: Coding error detected, it must be fixed by a programmer: Invalid value in set_user_preference() call, value is is too long for the value column Debug: \nError code: codingerror\n* line 1789 of /lib/moodlelib.php: coding_exception thrown\n* line 1636 of /grade/report/grader/lib.php: call to set_user_preference()\n* line 110 of /grade/report/grader/index.php: call to grade_report_grader::do_process_action()\n, referer: http://pcilms.mportfolios.net/grade/report/grader/index.php?id=291
[Thu Oct 10 20:24:26 2013] [error] [client 75.130.89.22] Default exception handler: Coding error detected, it must be fixed by a programmer: Invalid value in set_user_preference() call, value is is too long for the value column Debug: \nError code: codingerror\n* line 1789 of /lib/moodlelib.php: coding_exception thrown\n* line 1636 of /grade/report/grader/lib.php: call to set_user_preference()\n* line 110 of /grade/report/grader/index.php: call to grade_report_grader::do_process_action()\n, referer: http://pcilms.mportfolios.net/grade/report/grader/index.php?id=291&target=c3115&sesskey=TF6Dt0Lx1M&action=switch_minus
[Thu Oct 10 20:27:14 2013] [error] [client 75.130.89.22] Default exception handler: Coding error detected, it must be fixed by a programmer: Invalid value in set_user_preference() call, value is is too long for the value column Debug: \nError code: codingerror\n* line 1789 of /lib/moodlelib.php: coding_exception thrown\n* line 1636 of /grade/report/grader/lib.php: call to set_user_preference()\n* line 110 of /grade/report/grader/index.php: call to grade_report_grader::do_process_action()\n, referer: http://pcilms.mportfolios.net/grade/report/grader/index.php?id=291&target=c3115&sesskey=TF6Dt0Lx1M&action=switch_minus
root@offsite:/var/log/apache2#