Two night in a row after 12am lag skyrockets from 100 - 300ms to 2000+ ms while I'm playing World of Warcraft, but not with other more local game servers (e.g. Quake3 servers here in NZ).
If I cannot continue to play WoW after hours I'm going to have to switch ISPs, so I'm really hoping this is two isolated incidents - some kind of co-incidence :-(