I have just found this in the HTTPD error_log, but I don't know where to start fixing it, considering all I'm aware that's happened is that users have changed their AD passwords.
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[Mon Jan 27 17:37:56 2014] [error] [client 10.11.22.203] PHP Fatal error: Uncaught exception 'adLDAPException' with message 'Missing function support [bcmod]
http://www.php.net/manual/en/book.bc.php' in /var/www/dokuwiki.hayley-group.local/lib/plugins/authad/adLDAP/classes/adLDAPUsers.php:324\nStack trace:\n#0 /var/www/dokuwiki.hayley-group.local/lib/plugins/authad/auth.php(235): adLDAPUsers->passwordExpiry('sporter')\n#1 /var/www/dokuwiki.hayley-group.local/inc/auth.php(1092): auth_plugin_authad->getUserData('sporter')\n#2 /var/www/dokuwiki.hayley-group.local/inc/auth.php(223): auth_setCookie('sporter', 'CQnrcvq6OREf/7o...', true)\n#3 /var/www/dokuwiki.hayley-group.local/inc/auth.php(174): auth_login('sporter', 'Gronholm87', true, false)\n#4 /var/www/dokuwiki.hayley-group.local/inc/events.php(90): auth_login_wrapper(Array)\n#5 /var/www/dokuwiki.hayley-group.local/inc/events.php(196): Doku_Event->trigger('auth_login_wrap...', true)\n#6 /var/www/dokuwiki.hayley-group.local/inc/auth.php(116): trigger_event('AUTH_LOGIN_CHEC...', Array, 'auth_login_wrap...')\n#7 /var/www/dokuwiki.hayley-group.l in /var/www/dokuwiki.hayley-group.local/lib/plugins/authad/adLDAP/classes/adLDAPUsers.php on line 324, referer:
http://dokuwiki.hayley-group.local/doku.php?id=kyocera&do=login§ok=6bcef1cdec3099c036b8a5f9283a23f7
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