No issues in the internal EC2 network. At least, none that I could find. I guess that's the reason why ELB doesn't shift any traffic. The whole issue seems to be on the Internet facing network. Failing routers, maybe.

Pingdom still claims 100% uptime, but New Relic (which includes an equivalent pinging service) reports downtime from time to time. Around 25 timeout alerts into the last couple of hours.