This happens from time to time and will get me killed quite often.
When fighting a mob I will randomly be unable to use any skills on my keybinds (I have tried manually pressing them with the mouse pointer, bit hard to do in this game though).
At first I thought maybe the mob is silencing me, but it's not. I have to walk (can't run as unable to use any skills) away from the mob in hopes of not dying. I can Block, so I walk backwards and block the entire time till it resets. Shortly after I can walk normally again, too. At this point I know I'm out of combat and can go fight the mob again and usually I'm fine at this point.
Here's the odd part. I am not an WASD player, at all. I'm a long time gamer and have always used the Arrow keys and bind all of my spells around those keys, most of which are on the NumPad keys. (blame the 80s games!)
So the other day speaking with a friend of mine he mentioned his guild mate was having this exact problem and said "he doesn't use the arrow keys, but does use the NumPad keys, and he too is unable to use any skills until out of combat"
There is a problem that's causing this when pressing the NumPad keys within the game that locks down all of your skills until you are dead, or out of combat. (if you die you're stuck in Walk mode only and the Walk Mode keybind doesn't make you walk normal, you have to log out and back in to fix that additional part of the bug).
Zenimax - Please help research this bug, please. It's a really annoying one.