In MW 1.16alpha accessing your user prefs returns an error if $wgDefaultUserOptions is used (no matter which, I had many but it also happened with just 1). Error:

Global default is invalid for field gender

Backtrace:

#0 ...\includes\Preferences.php(1066): Preferences::getPreferences(Object(User))
#1 ...\includes\specials\SpecialPreferences.php(43): Preferences::getFormObject(Object(User))
#2 ...\includes\SpecialPage.php(559): SpecialPreferences->execute(NULL)
#3 ...\includes\Wiki.php(233): SpecialPage::executePath(Object(Title))
#4 ...\includes\Wiki.php(62): MediaWiki->initializeSpecialCases(Object(Title), Object(OutputPage), Object(WebRequest))
#5 ...\index.php(116): MediaWiki->initialize(Object(Title), NULL, Object(OutputPage), Object(User), Object(WebRequest))
#6 {main}

Version: 1.16.x
Severity: critical