We've tried (on the client end):
1) Clear browser history (cookies, cache, temp files, etc)
2) Try new browsers (Firefox, IE, Chrome)
3) Tried new computers (some people tried work and home, another tried via mobile)
On the back end:
1) Turn off all site caching (no more WP Supercache)
2) Make sure all the affected user accounts are linked via the unique ID to the ClickBank transaction (that's how Wishlist works, as far as I can see).
I filed a support ticket with Wishlist 6 hours ago and haven't heard anything yet. As we're providing forex signals and this information is critical to people making money, it's frustrating for us and our members.
Can anyone shed any light on this?