- Do you have the latest PayPal patch for 1.3.7 installed?
- Have you enabled debug logging in order to know what *actually* happened and why?
- Have you tested that all IPN communications are working properly?
- Have you attempted to reproduce the problem in order to determine whether it was a one-off situation or a consistent problem that all your customers will encounter?
- What addons/contributions do you have installed?


BTW: Posting "anyone?" isn't very helpful. A post with more information about the research you've done for answers to your problem ... would be a lot more useful ... and would be seen as more friendly, not to mention in better compliance with forum etiquette. Just a note for future.