I am seeing a fair amount of bounced, undeliverable email through SES today in US-West-1. I use a shared IP address for SES, and the one that seems to be assigned to my account seems to be the culprit.
Most of the returned email has included a specific diagnostic code:
However, the link above says that there are no issues with the IP address. A different Spamhaus search, though, indicates the IP address is on the CSS Blocklist.