net and gross price in admin not updating properly

Hi there, I downloaded a new version of 1.5.1 and I'm trying to set up taxes in the admin. I followed the tutorial for setting up UK VAT as usual and everything seems ok. But when I go to a product page and enter a product net price the gross just shows the exact same.

I can see from the page source that the javascript which holds the variable for the tax is set to 0 whereas it should be 20

tax_rates["2"] = 0;So I went and had a look at the collect_info file where that figure should come from and it seems that the query isn't picking up the tax rate properly.

function zen_get_tax_rate($class_id, $country_id = -1, $zone_id = -1) {
    global $db;
    global $customer_zone_id, $customer_country_id;

    if ( ($country_id == -1) && ($zone_id == -1) ) {
      if (!$_SESSION['customer_id']) {
        $country_id = STORE_COUNTRY;
        $zone_id = STORE_ZONE;
      } else {
        $country_id = $customer_country_id;
        $zone_id = $customer_zone_id;
      }
    }

    $tax = $db->Execute("select SUM(tax_rate) as tax_rate
                         from (" . TABLE_TAX_RATES . " tr
                         left join " . TABLE_ZONES_TO_GEO_ZONES . " za
                         ON tr.tax_zone_id = za.geo_zone_id
                         left join " . TABLE_GEO_ZONES . " tz ON tz.geo_zone_id = tr.tax_zone_id )
                         WHERE (za.zone_country_id IS NULL
                         OR za.zone_country_id = 0
                         OR za.zone_country_id = '" . (int)$country_id . "')
                         AND (za.zone_id IS NULL OR za.zone_id = 0
                         OR za.zone_id = '" . (int)$zone_id . "')
                         AND tr.tax_class_id = '" . (int)$class_id . "'
                         GROUP BY tr.tax_priority");

    if ($tax->RecordCount() > 0) {
      $tax_multiplier = 0;
      while (!$tax->EOF) {
        $tax_multiplier += $tax->fields['tax_rate'];
    $tax->MoveNext();
      }
      return $tax_multiplier;
    } else {
      return 0;
    }
  }

It looks like the if ($tax->RecordCount() > 0) evaluates to false because if I change the else to {return 50;} then the 50 shows up inthe javascript ok.

So I think it might be to do with the global $customer_country_id;

But I'm buggered if I can find where this is set. No mention of it in the files according to the search function of notepad++

I've been playing with this for hours now scratching my head. Whats going wrong? Any body know where the mysterious global comes from?