568008 Quick PayPal integration fix

Hi, I have just started having problems with the integration between PayPal payments through my checkout system and automatic activation of a users account when payment is complete. I have been receiving reports from users who say that their payment shows as cancelled once they complete the checkout process. They then can't sign into their account immediately because the database doesn't change the newly formed account from 'inactive' to 'active' - I've been having to do it manually. This PayPal integration problem is only an issue with new standard membership sign ups (£5 sign up fee). There have been no problems when customers place orders. I think it is a small task and may just require a change of one or two lines of bugged coding so there is a small budget but I would like to get the problem solved as quickly as possible. Thank you.