roundcube plugin

[Kuba]

Hi,
Ive just installed a calendar plugin to round cube . But when I trying 
add nev event I recive an error :

[13-Dec-2012 10:29:55 +0100]: DB Error: _doQuery: [Error message: Could 
not execute statement]
[Last executed query: PREPARE 
mdb2_statement_mysql_8e4694e56fff9fb627eae1884d7a550b275aa5203 FROM 
'SELECT e.*, COUNT(a.attachment_id) AS _attachments FROM events AS e\n 
LEFT JOIN attachments AS a ON (a.event_id = e.event_id OR a.event_id = 
e.recurrence_id)\n       WHERE e.calendar_id IN (\'1\',\'2\')\n AND 
e.event_id=?']
[Native code: 1140]
[Native message: Mixing of GROUP columns (MIN(),MAX(),COUNT(),...) with 
no GROUP columns is illegal if there is no GROUP BY clause]
  in 
/home/inside/domains/basenik/public_html/biuro/program/include/rcube_mdb2.php 
on line 285 (POST /?_task=calendar&_action=event?_task=&_action=)
[13-Dec-2012 10:29:55] PHP Fatal error: Unsupported operand types in 
/home/inside/domains/basenik/public_html/biuro/plugins/calendar/calendar.php 
on line 1089


Whats wrong ?

Best regards
Kuba
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