I have this problem since patch 1.19 and 1.19a went live.

Basically for me as Archer my action bar often shows things as Ready to Use but try using and you get a "Such a command cannot be used" my solution has just been to try and memorize the timers but still it gets annoying, especially when your near death and Second Wind shows as available when its not, this is a bug I had hoped would be fixed soon, it does it on Lancer and Gladiator too but for me its the worst on Archer, nearly every timer is off on it.