Export Failing

I am trying to export the catalogue from my site. But when it opens in Excell I get this message

Error: Incorrect key file for table '/tmp/#sql_ca0_4.MYI'; try to repair it<br />Error No: 126<br />SELECT p.product_id, pd.name, GROUP_CONCAT( DISTINCT CAST(pc.category_id AS CHAR(11)) SEPARATOR "," ) AS categories, p.sku, p.location, p.quantity, p.model, m.name AS manufacturer, p.image AS image_name, p.shipping, p.price, p.date_added, p.date_modified, p.date_available, p.weight, wc.unit, p.length, p.width, p.height, p.status, p.tax_class_id, p.viewed, p.sort_order, pd.language_id, ua.keyword, pd.description, pd.meta_description, pd.meta_keywords, p.stock_status_id, mc.unit AS length_unit, p.subtract, p.minimum, p.cost, GROUP_CONCAT( DISTINCT CAST(pr.related_id AS CHAR(11)) SEPARATOR "," ) AS related, GROUP_CONCAT( DISTINCT pt.tag SEPARATOR "," ) AS tags FROM `product` p LEFT JOIN `product_description` pd ON p.product_id=pd.product_id AND pd.language_id=1 LEFT JOIN `product_to_category` pc ON p.product_id=pc.product_id LEFT JOIN `url_alias` ua ON ua.query=CONCAT('product_id=',p.product_id) LEFT JOIN `manufacturer` m ON m.manufacturer_id = p.manufacturer_id LEFT JOIN `weight_class_description` wc ON wc.weight_class_id = p.weight_class_id AND wc.language_id=1 LEFT JOIN `length_class_description` mc ON mc.length_class_id=p.length_class_id AND mc.language_id=1 LEFT JOIN `product_related` pr ON pr.product_id=p.product_id LEFT JOIN `product_tags` pt ON pt.product_id=p.product_id AND pt.language_id=1 GROUP BY p.product_id ORDER BY p.product_id, pc.category_id;

Any ideas ??