Widget_exhibitors bug

This happens when I activate the plugin (on the whole installation).
Fatal error: Class ‘widget_exhibitors’ not found in /home/public_html/wp-includes/widgets.php on line 324.

List of other activated plugins:

• All Tagged Up 1.1
• Google Analyticator 6.4.5
• Google XML Sitemaps 3.3
• Gravity Forms 1.7.11
• Limit Login Attempts 1.7.1
• White Label Branding for WordPress 3.2.2 rev37652
• WPML CMS Nav 1.2.4
• WPML Media 1.0.1
• WPML Multilingual CMS 2.3.4

Current installed theme: http://themeforest.net/item/evento-event-management-wordpress-theme/488278