is this using server validation?
in the WA_ValidationToolkit/WAVT_Scripts_PHP.php file, find:
$knownDomsPat = "/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum)$/";
and ad the .ca domain to the list.
$knownDomsPat = "/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum|ca)$/";