Wassup version 1.6 looks very smart. but it doesn’t play nicely with PDO For WordPress (or at least the SQLite driver). There is a redundant call to mysql_* function in lib/main.php – but that’s just one of the issues.
it looks to me like the author has really over complicated some of the sql for the reporting functions. one of the queries contains from_unixtime() and a cast() function – all in mysql and php: loosely typed databases and languages!! why bother casting? and there seems to be quite a departure from the wordpress norm in storing unix timestamps rather than YYYY-MM-DD HH:MM:SS variants.
I have not managed to write a fix for this yet.