Sidebar : WordPress database error

hi,

i am getting this error in my side bar

WordPress database error: [You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1]
SELECT cat_id, cat_name FROM

and this my sidebar.php file code

<div class="right">
<?php if ( function_exists('dynamic_sidebar') && dynamic_sidebar(__('Right sidebar','theme171')) ) : else : ?>
<?php
 $link_cats = $wpdb->get_results("SELECT cat_id, cat_name FROM $wpdb->linkcategories");
 foreach ($link_cats as $link_cat) {
 ?>
							<div class="widget_style2" id="links_with_style">
								<h2 class="h2"><?php echo $link_cat->cat_name; ?></h2>
								<ul>
									<?php get_links($link_cat->cat_id, '<li>', '</li>', '', FALSE, 'rand', TRUE,
	TRUE, -1, TRUE); ?>
								</ul>
							</div>
<?php } ?>
							<div class="widget_style2" id="archives">
								<h2 class="h2"><?php _e('Archives','theme171'); ?></h2>
								<ul>
									<?php get_archives('monthly','10','custom','<li>','</li>'); ?>
								</ul>
							</div>

							<div class="widget_style2" id="meta">
								<h2 class="h2"><?php _e('Meta','theme171'); ?></h2>
								<ul>
									<?php wp_register('<li>', '</li>'); ?>
		<li><?php wp_loginout(); ?></li>
		<li><a href="http://validator.w3.org/check/referer" title="This page validates as XHTML 1.0 Transitional">Valid <abbr title="eXtensible HyperText Markup Language">XHTML</abbr></a></li>
		<li><a href="http://gmpg.org/xfn/"><abbr title="XHTML Friends Network">XFN</abbr></a></li>
		<li><a href="http://wordpress.org/" title="Powered by WordPress, state-of-the-art semantic personal publishing platform.">WordPress</a></li>
		<?php wp_meta(); ?>
								</ul>
							</div>
<?php endif; ?>
						</div>
					</div>
				</div>
				<img src="<?php bloginfo('stylesheet_directory'); ?>/images/spacer.gif" alt="" align="top" style="width:10px; height:14px;"/>
			</div>
		</div>