If you've been dealing with lag issues in World of Tanks since patch 0.6.4 launched last week, Wargaming.net recommends that you read their latest developers' blog entry. It explains the nature of the lag issues and offers a suggestion on how to fix the problem:

"If you experience heavy lag, we recommend that you find your “trace route” to our game server. In Windows, start a Command Prompt (Start -> Run -> cmd), then type 'tracert 174.34.231.132.' This should also work for any third-party tracking application. Send the results to our Support Services by opening a support ticket. We are grateful for your cooperation and patience in helping us resolve these issues."