Similar problem. Since last night (not been on for a while) I seem to be able to play for about 5 to ten minutes then it lags ( I can move but everything else stops dead) and then cuts me off the internet entirely. Black screen with an error message saying the client is unable to connect.
I figured it was probably some sort of ISP issue, but everything’s absolutely fine when not playing GW2. I put GW2 back on, 5-10 minutes, bang, I’m cut off again. I don’t quite understand how it can completely cut my connection to the internet. On an EU server so I don’t think it’s just a US thing.