londrum - 1:06 pm on Nov 30, 2010 (gmt 0)
sounds like there are no values to grab under those names (lat and lng).
while (have_posts()) : the_post();
$var = get_post_meta($post->ID, "var", true);
$lat = get_post_meta($post->ID, "lat", true);
$lng = get_post_meta($post->ID, "lng", true);
if that doesn't print anything then check that there are actually some custom field values set for those posts under those names. sounds like there isn't.