I was having this issue. Start shortcut, game updates, login screen, to play screen, starts to load then boom. No window on my machine would work anymore with the mouse. Turning off game mode in Windows 10 did nothing. I was able to close the client with ctrl-shift-esc arrowing down to Guild Wars client and hitting delete key.
I looked for command line options (https://wiki.guildwars2.com/wiki/Command_line_arguments) and found a way to disable settings around DirectX config. I started the game using a different shortcut with -windowed -dx9 and it came up.
I hope this helps.