Thread:Project:Support desk/error when accessing user preferences

When a user attempts to click the "My Preferences" link the get this error

Internal error lobal default '' is invalid for field editfont Backtrace:
 * 1) 0 /srv/http/SupportWiki/includes/Preferences.php(1152): Preferences::getPreferences(Object(User))
 * 2) 1 /srv/http/SupportWiki/includes/specials/SpecialPreferences.php(43): Preferences::getFormObject(Object(User))
 * 3) 2 /srv/http/SupportWiki/includes/SpecialPage.php(559): SpecialPreferences->execute(NULL)
 * 4) 3 /srv/http/SupportWiki/includes/Wiki.php(254): SpecialPage::executePath(Object(Title))
 * 5) 4 /srv/http/SupportWiki/includes/Wiki.php(64): MediaWiki->handleSpecialCases(Object(Title), Object(OutputPage), Object(WebRequest))
 * 6) 5 /srv/http/SupportWiki/index.php(117): MediaWiki->performRequestForTitle(Object(Title), NULL, Object(OutputPage), Object(User), Object(WebRequest))
 * 7) 6 {main}

our versions are as follows MediaWiki	1.16.0 PHP	5.3.5 (apache2handler) MySQL	5.1.54-log

my Wiki is internal to my organization so I am unable to provide an URL. I enabled MySQL logging and clicked the pref page and not able to determine where this value is set (or in a case maybe not set) I did find the Preferences.php that contained

$defaultPreferences['editfont'] = array(                                       'type' => 'select',                                        'section' => 'editing/advancedediting',                                        'label-message' => 'editfont-style',                                        'options' => array( wfMsg( 'editfont-default' ) => 'default', wfMsg( 'editfont-monospace' ) => 'monospace', wfMsg( 'editfont-sansserif' ) => 'sans-serif', wfMsg( 'editfont-serif' ) => 'serif', )                               );

any help would be greatly appreciated.