Next Post and Previous Post links in single.php

Hi. I’ve just upgraded from 2.3 to 2.6 (kept putting it off) and all is well except for one thing: the next and previous links at the bottom of my posts are missing.

At the bottom of each post, I had <<[previous post title] and [next post title]>> links. Now I do not.

This is the code towards the bottom of my single.php file, with some css removed for clarity:

<?php previous_post_link('<span class="meta-nav">&laquo;</span> %link') ?>
<?php next_post_link('%link <span class="meta-nav">&raquo;</span>') ?>

My best guess is that something there is deprecated but I haven’t been able to figure out what.

ETA: I did try to replace previous_post_link with previous_post (and next, etc.) but that doesn’t work, either.

Any help? Thanks in advance. I’ve looked through the other support posts on missing previous/next links in 2.5+ but they seem mainly to be about index and archive pages, not individual posts.