Major Issue User Group After Purchase

Hello all - I have a strange issue.
I have certain products set up to grant a user group after purchase.
They are confirmed by PayPal IPN (This works for setting the status)
However...
The groups do NOT assign after purchase is flagged as confirmed by PayPal.

IF however I go into the order AFTER the fact, change the status from Confirmed to Created...
and then BACK to confirmed... the groups assign just fine.

HELP!

Hi Nicolas! Thank you for getting back to me!

Joomla 2.5.6
Hika Business 1.58 (we just bought it a couple days ago)

The group plugin IS enabled and set to 'Unregistered/Public' access on our system. (I even re-copied it from the 1.5.8 distro after having read some of the forums on here to make sure it was a clean unadulterated copy, and then disabled/re-enabled it.)

As per your PM to me I will PM you back with an admin login for the back end as well as an FTP login - if you'd be willing to take a look and get back to me that would be FANTASTIC. (Sorry I wasn't more informative in my first post - I was a bit frazzled at 1AM my time. LOL!)

In the meantime, the site has gone live, and I've removed the group limits from all items - I don't have a problem with you setting up test categories/products if you need to try to do anything - just let me know what I need to do to help you help me.

Thank you so much!