I've been having horrible lag (1k +ms) from the US this weekend. I heard some others complaining about it as well.

After doing some checking, all AT&T internet users in the US seem to be having this problem while connecting to private servers. I won't link the post, but there's a discussion on a vanilla private server with several AT&T customers having this same problem.

They say that a VPN solves the problem. Unfortunately, Warmane appears to block the VPN I use (Pingzapper)- I've sent them an e-mail asking support to allow it, but I haven't heard back from them.

But anyway, if you use AT&T internet from the US and have really bad lag, this is almost certainly the cause.