Well, since, I'm the maintainer of all of those modules, I don't really have anywhere to pass it on to :-). Testing as we speak, I'll update when I have an answer and please /msg if you find something out in the meantime.

update1

Very, very odd. I got the same fubared results you did. But when I run the test below (which uses all the same SQL as yours), everything is copacetic. More later.

#! /usr/bin/perl -w
use strict;
use DBI;
use FindBin;
open my $fh, '>', $FindBin::Bin . '/Tanktalus';
print $fh ("DATE,NUMBER\n2005-05-16,2\n2005-05-17,4\n");
close $fh;

my $dbh = DBI->connect("dbi:CSV(RaiseError=1):csv_eol=\n");
for my $sql(<DATA>){
    my $sth = $dbh->prepare($sql);
    $sth->execute;
    $sth->dump_results if $sth->{NUM_OF_FIELDS};
}
__END__
SELECT date,number FROM Tanktalus
SELECT SUM(number) from Tanktalus
UPDATE Tanktalus SET number=8 WHERE date='2005-05-17'
SELECT date,number FROM Tanktalus
SELECT SUM(number) from Tanktalus
SELECT number FROM Tanktalus WHERE date = '2005-05-17'
[download]

update2

Ok, I can reproduce the error by using placeholders for the update in the script above. It's a SQL::Statement problem. Fix coming by morning.

update3

Ok, I found and fixed the bug in SQL::Statement. Please try grab the latest from the SVN repository and let me know if it works for you. I thanked you for the bug report in the Changes log of the distro.