Looks like PayPal was having some issues handling PayPal account-based checkout payments this afternoon. This would not have affected IPN and post-payment order processing at our end, but it could have been preventing some buyers from completing a PayPal checkout in the first place. PayPal reports the issue has been resolved as of 3:05pm PST.
(Live Site-631)  Resolved - Intermittent errors for PayPal Website and APIs - Feb 17
02-17-2009 01:36 PM
PayPal_Updates PayPal_Updates Administrator writes...
 Resolved: This notification is to inform you that the following intermittent issue with PayPal Website Payments Standard and the PayPal Express Checkout APIs has been resolved as of Feb 17, 3:05 PM PST (Feb 17, 11:05 PM GMT).
(Sent Feb 17, 3:23 PM PST by AP)
Service: PayPal Live Site
During the time listed below you may have experienced the following:
Intermittent errors with Website Payments Standard (Payment could not be completed) and intermittent HTTP 500 error for Express Checkout APIs.
- Website Payments Standard
- Express Checkout
- Signature Authentication
- SSL Certificate Authentication
Start Time: Feb 17, 12:43 PM PST (Feb 17, 8:43 PM GMT)
End Time: Feb 17, 3:05 PM PST (Feb 17, 11:05 PM GMT)
We apologize for any impact caused by this incident.
PayPal Merchant Technical Services
If you have questions, contact PayPal Merchant Technical Services by filing a ticket under contact support (refer to ID: Live Site-631) at https://www.paypal.com/mts/.
 Update: PayPal continues to work on the issue and will provide updates as they become available.
(Sent Feb 17, 3:02 PM PST by AP)
 Notification: This notification is to inform you of the following intermittent issue with PayPal Website Payments Standard and the PayPal Express Checkout APIs.
(Sent Feb 17, 1:37 PM PST by AP)