[Buddypress] Ajax Chat Error Message

I installed the newest Ajax Chat for Buddypress, but I get only errors when opening the chat or shoutbox windows. Does anyone know why and how to fix this?

Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource in /is/htdocs/domain/wp-content/plugins/buddypress-ajax-chat/bp-chat/chat/lib/class/CustomAJAXChat.php on line 216

Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in /is/htdocs/domain/wp-content/plugins/buddypress-ajax-chat/bp-chat/chat/lib/class/CustomAJAXChat.php on line 240

Warning: Cannot modify header information - headers already sent by (output started at /is/htdocs/domain/wp-content/plugins/buddypress-ajax-chat/bp-chat/chat/lib/class/CustomAJAXChat.php:216) in /is/htdocs/domain/wp-content/plugins/buddypress-ajax-chat/bp-chat/chat/lib/class/AJAXChatHTTPHeader.php on line 36

Warning: Cannot modify header information - headers already sent by (output started at /is/htdocs/domain/wp-content/plugins/buddypress-ajax-chat/bp-chat/chat/lib/class/CustomAJAXChat.php:216) in /is/htdocs/domain/wp-content/plugins/buddypress-ajax-chat/bp-chat/chat/lib/class/AJAXChatHTTPHeader.php on line 37

Warning: Cannot modify header information - headers already sent by (output started at /is/htdocs/domain/wp-content/plugins/buddypress-ajax-chat/bp-chat/chat/lib/class/CustomAJAXChat.php:216) in /is/htdocs/domain/wp-content/plugins/buddypress-ajax-chat/bp-chat/chat/lib/class/AJAXChatHTTPHeader.php on line 41