Error When I Click "Manage Subscriptions" Email Link

I recently installed Subscribe By Email...

1. I have a job board plugin that goes under the post type of "Job Listings." The point is for users to be notified by email whenever a new job gets published to the job board.

2. To test things out, I added one of my email addresses and got a new job notification email without a problem.

3. However, while testing the "manage subscriptions" link at the bottom of that email, i get the following error (see screenshot also)

Warning: in_array() [function.in-array]: Wrong datatype for second argument in /home4/diablo2/public_html/writertown.com/wp-content/plugins/subscribe-by-email/front/manage-subscription.php on line 87
id="sub_post_type-job_listing" name="sub_post_types[]" value="job_listing"> Job Listings

4. But here's the interesting part: If i click the check-box (see screenshot) and click "Save", then the error disappears and everything works beautifully from the SECOND time onwards. From that point on, i can click the link as much as i want and that error is gone...

5. I tried more than one job, more than one email address, and even built another subscription page. Same deal.

Have you guys seen this before? (fyi, im not code-friendly).

P.S. I have version 2.8.1.1 and the latest WordPress version.

Thanks