Inputs cutting eachother out

Here’s the code

var bulletPrefab:Transform;

function Update ()
{

if(Input.GetButtonDown("Fire Up"))
{
	var upBullet=Instantiate(bulletPrefab, GameObject.Find("spawnUp").transform.position,Quaternion.identity);
}
if(Input.GetButtonDown("Fire Right"))
{
	var rightBullet=Instantiate(bulletPrefab, GameObject.Find("spawnRight").transform.position,Quaternion.identity);
}
if(Input.GetButtonDown("Fire Left"))
{
	var leftBullet=Instantiate(bulletPrefab, GameObject.Find("spawnLeft").transform.position,Quaternion.identity);
}
if(Input.GetButtonDown("Fire Down"))
{
	var downBullet=Instantiate(bulletPrefab, GameObject.Find("spawnDown").transform.position,Quaternion.identity);
}

all the buttons work, it instantiates everything correctly under any single direction move or stationary HOWEVER… sometimes they wont work when moving diaganoly (two motion inputs going at once)

ie right fire wont work if im also going up and right
down and left fire wont work if im also going down and to the left
etc

I’m using the standard first person controller that comes with unity4

I’ve turned on and off the platform follow, jump, and slide.

I already checked to make sure there weren’t overlapping key inputs or something

I already checked to make sure the spawn points weren’t too close to the character input thingy and causeing some weird collision issue

I don’t know what else to look at

The problem is the number of keys that were being pressed at one time. Some keyboards have a limit on the total number of keys pressed, and some have limits on the total number of keys pressed in a certain group. Keyboards specifically made for gaming tend to allow more keys to be pressed than a normal keyboard, but can still have limitations. When you hit the cap, it will appear as if the game isn’t accepting the input or ignoring it, where in fact the hardware is not registering the keys pressed after the limit was reached. A good way to check is to use a keyboard tester (such as one here) and see if the keys assigned in your game are all showing up and not being cut off by the keyboard itself.