Arena.Net has announced that a Guild Wars 2 beta stress test will be conducted for a limited number of hours on Monday, May 14th from 11:00 a.m. PDT to 6:00 p.m. PDT. The goal of the test is to pack the servers with players to ensure stability.
This special test event is open only to Pre-Purchase customers who have registered their accounts. With your help, we can conduct important tests and address some of the issues we identified during our first Beta Weekend Event. During this event, all you need to do is play normally with a new or existing character on your Beta account using the same game client. Please note that since this is a stress test of our servers, you may experience some in-game performance issues. If you’ve pre-purchased Guild Wars 2 and wish to participate in the stress test, we recommend that you register the account and download the game client.
Source: GW2 Facebook page