You can get the last insert id from mySQL on a per-handle basis by asking for:

my $new_id = $dbh->{'mysql_insertid'};

Which should get around the problem, unless you're using Apache::DBI or something else that pools database handles.

update: remembered something i saw in the lower reaches of Class::DBI::Extension: you can lock a mysql table using:

$dbh->do('LOCK TABLES mumble WRITE');

and later

$dbh->do('UNLOCK TABLES');

But it's a rather drastic thing to do, and one of the main reasons some people are rude about MySQL.