Blank Page on Many Old Posts

Hi,

I’d like to know why do I get blank pages on many of my old posts? When I try to edit some of my old posts with blank page and click save I get these messages

WordPress database error: [Unknown column ‘link_’ in ‘order clause’]
SELECT * , IF (DATE_ADD(link_updated, INTERVAL 120 MINUTE) >= NOW(), 1,0) as recently_updated FROM wp_links INNER JOIN wp_term_relationships AS tr ON (wp_links.link_id = tr.object_id) INNER JOIN wp_term_taxonomy as tt ON tt.term_taxonomy_id = tr.term_taxonomy_id WHERE 1=1 AND link_visible = ‘Y’ AND ( tt.term_id = 30 ) AND taxonomy = ‘link_category’ ORDER BY link_

Warning: Cannot modify header information – headers already sent by (output started at /home/sdp/public_html/wp-includes/wp-db.php:517) in /home/sdp/public_html/wp-includes/pluggable.php on line 770

I’ve read the FAQ Troubleshooting and searched the past support tickets and none have similar problem as mine.

Can someone please tell me what is causing these errors, and how do i rectify this problem.

Also this happens when I replied my comments.

Thank you.