(I do not think this is a duplicate of 483. I do not have any extra security software on my Mac).

On my macbook pro, I do not have reliable mouse buttons (trackpad with the "button" just being a harder trackpad press). So, I have everything mapped to keys.

In particular, "use" is mapped to a key. If I drink a potion, or eat food, then I have to hold down the "q" key – and apparently, that – having to hold it down for a while to activate something – causes it to become "stuck".

The most reliable way to unstick it is to command-tab out and back in. Sometimes, it will unstick on it's own. Hilarity ensures if I'm in creative mode and trying to drink a potion, and it auto-repeats the potion forever . Or, as happened once, repeatedly throws a splash potion after I try to stop.

But even when it unsticks on it's own, and 90+% of the time when I switch to another app and back, movement keys (the arrows for me) have a "delay"/"lag" – not only is there a delay before I start moving, but the movement seems "heavy", and will continue a little past the point where I release it.

Two app switches and back will solve this. And, oddly, 98+% of the time it is solved for my entire play session until I restart the client.

Now, there is one other case where this happens. Our base has a minecart elevator – minecarts every 4 spaces in a vertical tube suspended by ladders. I can easily go upwards if I press and release Q for each minecart. However, if I hold Q down to go all the way up, then the "use" will stick – and upon reaching the top of the shaft, I'm trying to place whatever block was in my active hotbar slot.

Based on this, I'm suspecting that it is something about the keyboard input state; since this only happens on mac and not PC's or Linux, I'm suspicious of LWJGL.

This happens with or without optifine; with or without Optifine's input priority adjustment settings. I have a multicore CPU, and this has happened as far back as 125 single player; currently I only play SMP and it happens in 147 and 151, creative or survival.