This issue started for me last night and even after trying eventhing suggested in previous threads on this topic and similar issues I couldn't fix it. Eventually I went into my firewall to make sure the launcher was still allowed and I found it was not. I had a windows update right before the problem started which might have effected it, so double check your firewall settings and allow the Guild Wars 2 laucher both private and public accses. Once I allowed both of those and enabled them in the inbound rules I haven't had any dissconnect issues. This may not be the root of everyones problem but its worth checking.