Lag spikes/Packet loss

Hello,

since 2 weeks I'm getting random lag spikes on Icecrown Warmane. I didn't had problems for months since I started here. My average ping to the server is 50-60ms, but sometimes it jumps to 200ms. I've checked my internet connection and provider with PingPlotter where everything is okay. Other games work well too. On Warmane it feels like a packet loss and a disconnect for 1-3sec. After that the game continues. I'm getting these spikes every 5-10min and it is really annoying in raids. Are there currently technical issues from the server or what can I do to find out the problem ?