Sql syntax problem

hi,
function signup_costs_total($nid, $uid){
$sql = 'SELECT sv.value, sv.choices, sf.title, sf.is_costed, sf.amount, sf.type
FROM {signup_fields} as sf INNER JOIN {signup_values} as sv
ON (sf.fid = sv.fid) WHERE sv.nid = %d AND sv.uid = %d';
$r = db_query($sql, $nid, $uid);

....more code etc

I have been staring at the above for about an hour.. so here is the problem
It does not return a row. The record is there because I have used the same sql in a mysql client. the variables $nid and $uid have the correct values to bring back a row

Am I missing something obvious ?