I’m also having the similar keyboard issues as many in this thread. The keyboard input stops functioning, however mouse control continues to be fine. If I Alt-Tab out of GW2 into another program / desktop, the keyboard is working fine there. I also use a Razer gaming keyboard, and that input also stops functioning at the same time.
The only fix is to log out, and restart. Of course, I now have had to fight the final Mordremoth fight 4-5 times as when I log out, I have to restart the whole darn thing. The error seems to happen when a frantic fight is happening, with lots of keyboard clicks, double clicks, etc…