Modifiers causing internal compilation error

Question

My modifiers are throwing internal compilation errors: Internal compiler error: Identifier type not expected in expression context.

modifier critical {
    if (mutex) throw;
    mutex = true;
    _;
    mutex = false;
}

function createPlayer() {
    critical; 
    var player = players[msg.sender];
    if (player.ready) { throw; }
    player.ethaddress = msg.sender;
    player.creationdate = block.timestamp; 
    player.balance += msg.value;
}

Answer 1

function createPlayer() critical {
// Not
function createPlayer() {
    critical; 

Answer 2

Modifiers are specified after the function, like:

function createPlayer() critical {
    ...
}