"freezing" without freezing. unresponsive keyboard

The game is frequently "freezing", as in becomes entirely unresponsive to most keyboard commands. It affects movement, opening menus, and "esc," but ALSO affects the ability to alt+tab, or to use ctrl+alt+del. 

It effectively freezes, but graphics and such continue as if everything is normal. This has happened in Arlathan forest, at the Veil Jumper camp, in the Lighthouse, and at the ritual site. It makes the game very difficult to play. Restarting the game does not resolve the issue.