I am running into a very similar problem, also on Bluehost.com. I haven't found a solution, but perhaps we can share notes and figure this out. I have checked many times that my IPN processing in PayPal is configured properly, with UTF-8 and notifications on, according to the settings at:
I had PayPal enrollment working on my server with Moodle 1.9, but since I've done a fresh install of Moodle 2.2.x I have not had any success. So it seems unlikely that this is a Bluehost issue.
In my situation payment is processed and in PayPal the transaction status is "completed" in the PayPay IPN history. The Moodle admin email account and the user email account get notifications that the payment is processed successfully. However the learner is not enrolled in the course.
Is this is what you are seeing, or did you have another variation? Looking through previous forum posts it seems that the PayPal enrollment can fail in several different ways. Thanks in advance....