Fatal Error: Undefined Function: userpoints_role_userpoints()

Issue Summary

I am new to Drupal and this is my first support request, so please forgive me if I am not doing this right. Here is my issue:

I am using Drupal 5.7 I installed the UserPoints module, and it works great, I then installed the Referral Contributed Module, and everything works up until the point where I try to create a new account, I get the following error message

Fatal error: Call to undefined function: userpoints_role_userpoints() in /home/xxxxxxxx/public_html/xxxxxxxxxxx/sites/all/modules/referral/referral.module on line 217

When I uninstall the referral module I am then able to create new accounts. I am totally unsure what to do. I am not sure if this is a UserPoints issue, a Referral Module issue or I am missing something very obvious. Line 216 and 217 of the referral.module are listed below. PLEASE HELP!

// Check to see if the role needs to be elevated
userpoints_role_userpoints('points after', 0, $cookie[$uid], '');