Hmmm. Here's what I did just now on one of my blogs at http://vkaryl.net/whispers -
<?php comments_popup_link('Click Here to Comment »', '1 Comment - Click Here to Add a Comment »', '% Comments - Click Here to Add a Comment »'); ?>
It displays just fine.... Now, keep in mind that your original is a bit different than mine: I have NO clue what the _t is, possibly it's theme specific, and if that's the case, and the above tweak doesn't work for you, then you might have to try this instead:
<?php comments_popup_link(_t('Click Here to Comment'), _t(1 Comment - Click Here to Add a Comment'), _t('% Comments - Click Here to Add a Comment')); ?>
In fact, you might try that last one first, just because it IS different from the theme I tried it in.... and if neither of them work, then you might have to contact the theme author, or hope that someone familiar with the theme and tweaking it happens by and has a better answer for you.