This has been noticed by a lot of folks in RK2, don't know if it's also happening on RK1.
Every day RK2 shudders at exactly 7:00pm my time (Central time USA). This is coincidentally exactly 12:00 (midnight) GMT/UTC time. For approximately 3-5 minutes the game server will lag tremendously often causing a few to disconnect. The chat server, however, is fine. My guild, group and other channels continue to chat freely without lag, usually discussing what we've named the "Witching Hour". The problem is severe enough that I've taken to watching the time and trying to be somewhere safe when this happens instead of fighting mobs in a mission...