Maintenance for the week of July 13:
• PC/Mac: No maintenance – July 13
The issues on the North American and European PlayStation® megaservers have been resolved at this time. If you continue to experience difficulties at login, please restart your client. Thank you for your patience!
The problem probably is server software. Some things are difficult or impossible to do concurrently and may start to bottleneck when load gets high enough on any hardware. (Or start to fail and roll back or just get corrupted.)