Web3js – Calling Smart Contract Function: Fixing ‘this._eth.call Is Not a Function’

i went throught the greeter example in here https://www.ethereum.org/greeter and i deployed the smart contract under ropsten test net.

Now im trying to call it from a web page using web3.

var greeterAddress = '0xbc15fCDef6F6FAbAd4097816006523626c10a685';
        var abi = [{ constant: false, inputs: [], name: 'kill', outputs: [], type: 'function' }, { constant: true, inputs: [], name: 'greet', outputs: [{ name: '', type: 'string' }], type: 'function' }, { inputs: [{ name: '_greeting', type: 'string' }], type: 'constructor' }];
        
        var greeter2 = new web3.eth.contract(abi).at(greeterAddress);        
        
        console.log('Calling the smart contract');
        var result = greeter2.greet();
        console.log(result);

i keep getting while calling:

var result = greeter2.greet();

the following error:

Uncaught TypeError: this._eth.call is not a function
    at c.call (inpage.js:14300)
    at c.execute (inpage.js:14300)
    at send (ex.html:32)
    at HTMLButtonElement.onclick (ex.html:14)

which step should i take to make sure the contract doen't have any initilization problem?
For what i have seen by looking around at examples this should work without problems.

More info: I have another piece of code sending ETH to an address and works just fine, so web3 should be properly installed (version is 0.2x.x.)

EDIT Final working solution:

 var greeterAddress = '0xbc15fCDef6F6FAbAd4097816006523626c10a685';
        var abi = [{ constant: false, inputs: [], name: 'kill', outputs: [], type: 'function' }, { constant: true, inputs: [], name: 'greet', outputs: [{ name: '', type: 'string' }], type: 'function' }, { inputs: [{ name: '_greeting', type: 'string' }], type: 'constructor' }];
        
        var greeter2 = web3.eth.contract(abi).at(greeterAddress);        
        
        console.log('Calling the smart contract');
        greeter2.greet(function (error, result) {
            if (!error)
                console.log(result)
            else
                console.error(error);
        });