Just a quick update:

It appears we are being/have been attacked by a DDoS attack (huh?) against our VPS.
Although we're not 100% certain, it appears to be an attack because the packets are coming from a certain few IPs and are coming in at a steady rate, and the source port increases every two packets, making it seem automated in nature.

It appears our efforts to mitigate the attacks have been successful, and the site appears to be up and running again. We are extremely sorry for the downtime and hopefully this won't happen again, and if so, should be resolved quicker.