Invalid group id

(/usr/local/www/sites/forum.bong.com.au/FUDforumdata/include/theme/default/db.inc:78
/usr/local/www/sites/forum.bong.com.au/FUDforumdata/include/theme/default/private.inc:127
/usr/local/www/sites/forum.bong.com.au/FUDforumdata/include/theme/default/ssu.inc:30
/usr/local/www/sites/forum.bong.com.au/htdocs/adm/admmassemail.php:62
) 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') AND users_opt>=64 AND (users_opt & 64) > 0' at line 1
Query: SELECT id, email FROM fud26_users WHERE id IN() AND users_opt>=64 AND (users_opt & 64) > 0
_GET: array ( 'SQ' => '6b18635c13f239f6ca3607dac74db672', )
_POST: array ( 'SQ' => '6b18635c13f239f6ca3607dac74db672', 'pm' => '1', 'group' => '-1000000001', 'subject' => 'test', 'body' => 'test', 'btn_submit' => 'Send', )
Server Version: 4.1.12-log
[Referring Page] http://forum.bong.com.au/adm/admmassemail.php?&SQ=6b18635c13f239f6ca3607dac74db672

System Configuration
PHP built On: 	FreeBSD kusanagi.bong.com.au 5.4-RELEASE FreeBSD 5.4-RELEASE #0: Sat Jun 4 00:30:43 EST 2005 dean(at)kusanagi(dot)bong(dot)com(dot)au.:/usr/obj/usr/src/sys/DEAN0 i386
Database Version: 	4.1.12-log
PHP Version: 	4.4.2
Web Server: 	Apache/2.0.55 (FreeBSD) PHP/4.4.2 mod_perl/2.0.2 Perl/v5.8.7
WebServer to PHP interface: 	apache2handler
WebServer User/Group: 	80 / 80
Forum Version: 	2.7.4
Relavent PHP Settings: 	
Safe Mode: 	OFF
Open basedir: 	none
Display Errors: 	ON
File Uploads: 	ON
Maximum File Upload Size: 	2M
Magic Quotes: 	ON
Register Globals: 	OFF
Output Buffering: 	No
Disabled Functions: 	none
PSpell Support: 	No
Zlib Support: 	Yes