The same thing happened to me last night. I tried upgrading from X2 Producer to X3 Producer and it got stranded on the processing screen. I have a receipt showing that the money went through with Paypal, however, I don't have any links in my account to download the new X3 producer. Kind of bummed but hey, it's technology, it's not perfect.
If any of the admins could hook me up before the weekend is over that would be great. If not, I guess I will have to call support on Monday.
Cheers