Custom fields not displaying in Post Preview mode

Hello, I'm having trouble with my custom fields displaying in the preview window when I go to publish a custom post. I was getting a 404 error at first, which was fixed by saving the permalink settings. Now, however, the post title displays in preview mode, but no custom content displays along with it. I have two custom fields within my custom post, neither of which are working.

I've been looking all over for a fix but to no avail. Anybody have any similar problems?

I'm displaying my custom fields on the front end with:

$portfolioContent = get_post_meta($post->ID, 'wpcf-portfolio-content', true);
echo $portfolioContent;

Thanks for any help.

Colin