cheezykins

whichever file is calling $wpdb->linkcategories, possibly one of your theme files. I was calling it in my theme.

Ok, it seems they’ve joined the categories tables together, so a simple fix for me was changing
$wpdb->get_results('SELECT cat_id, cat_name FROM ' . $wpdb->linkcategories);

to this

$wpdb->get_results('SELECT cat_id, cat_name FROM ' . $wpdb->categories . ' WHERE link_count > 0')

Ive just registered myself because of this problem.

It would appear that $wpdb->linkcategories is NULL in 2.1, hence breaking any SQL that relies upon it. This doesn’t seem to be a documented change so I’m not sure what’s causing it. :/