There is a bug after updating cPanel, when you try to login in Horde you see this error:
Warning: NLS::include_once(/usr/local/cpanel/base/horde/config/nls.php) [function.NLS-include-once]: failed to open stream: Permission denied in /usr/local/cpanel/base/horde/lib/Horde/NLS.php on line 91
The steps to solve this problem:
chattr -i /usr/local/cpanel/base/horde/config/nls.php
chattr -i /usr/local/cpanel/base/horde/config/prefs.php
chattr -i /usr/local/cpanel/base/horde/imp/config/conf.php
chattr -i /usr/local/cpanel/base/horde/imp/config/conf.xml
/usr/local/cpanel/bin/update-horde --force
rm -f /etc/vmail/*
/scripts/updateuserdomains