Recent posts on Twitter have indicated that Americas Cardroom was not the only online poker site attacked by DDoS hackers this week (see previous report).
Very little detail is currently available but it appears that:
On August 9 PartyPoker advised players: “Apologies for the technical difficulties, we are working to rectify, the site has been targeted with a DDoS attack from third parties. We hope to resume normal business very soon and will keep you updated. Thank you for your patience.”