okay, one line of code, seems good to me, but wont work
mysql_query("UPDATE things SET thing1 = 'no' WHERE userid = '$userid' AND thing1 = 'yes'");
It looks fine to me...
Do like this: mysql_query("UPDATE things SET thing1 = 'no' WHERE userid = '$userid' AND thing1 = 'yes'") or die(mysql_error());
to see if it returns an error.
/Staffan