Same error here but upgrade from 7.10 to 8.04 was performed.
Other user having same error: https://answers.launchpad.net/ubuntu/+question/31050
///usr/share/gnome/help/blackjack/el/blackjack.xml:402: parser error : Entity 'Βοήθεια' not defined <para><guimenuitem>Προτιμήσεις&Βοήθεια;</gui
Same error here but upgrade from 7.10 to 8.04 was performed.
Other user having same error: https:/ /answers. launchpad. net/ubuntu/ +question/ 31050
///usr/ share/gnome/ help/blackjack/ el/blackjack. xml:402: parser error : Entity 'Βοήθεια' not defined
<para> <guimenuitem> Προτιμήσεις& Βοήθεια; </gui