Update:
I *think* the problem began when running this query in the database for the shoutbox:
CREATE TABLE `shoutbox` (
`shoutid` int(11) NOT NULL auto_increment,
`userid` int(11) NOT NULL default '0',
`shout_text` text NOT NULL,
`timestamp` int(11) NOT NULL default '0',
PRIMARY KEY (`shoutid`)
) TYPE=MyISAM;
Since then my 'active users today' doesn't seem to be working either
Anyone able to help please?