Just wanted to drop by and point out that Mike Little graciously answered this for me. Here’s what he wrote:
The plugin only wraps calls to the_time() (and get_comment_date()) and adds the Hebrew date to the end. My theme uses the_date().
To fix it with my theme, you need to replace the call to the_date() with a call to the_time().
In index.php around line 14 replace
<?php the_date('','<h2>','</h2>');?>
with
<h2><?php the_time('F jS, Y') ?></h2>
Then in page.php at the end of line 16 replace
@ <?php the_time() ?> on <?php the_date() ?>.
with
on <?php the_time('F jS, Y') ?>.