— A.makeCall({gas:300000}); // NO ERRORS
— A.sender(); // 0x0000000000000000000000000000000000000000 AS EXPECTED
— A.myVar(); // 0 AS EXPECTED
— B.sender(); // addressA AS EXPECTED
— B.myVar(); // 1 AS EXPECTED

— A.reset({gas: 300000}); // NO ERRORS;

— A.sender(); // 0x0000000000000000000000000000000000000000 AS EXPECTED
— A.myVar(); // 0 AS EXPECTED
— B.sender(); // 0x0 AS EXPECTED
— B.myVar(); // 0 AS EXPECTED

— A.makeCallCode({gas:300000}); // NO ERRORS
— A.sender(); // 0x0000000000000000000000000000000000000002 Oops! It looks like there was no access to msg.sender and sender variable was assigned argument x instead.
— A.myVar(); // 0 Oops! Nothing was assigned, because of the ↑
— B.sender(); // 0x0 AS EXPECTED
— B.myVar(); // 0 AS EXPECTED

— A.reset({gas: 300000}); //ALL KIND OF ERRORS; WTF IS GOING ON HERE? NO MATTER HOW MUCH GAS I SUPPLY IT STILL FAILS. https://testnet.etherscan.io/tx/0x6654b6739f55690c7114fa9e8cfb7a5959e73d60c37782aee4e211487de859f2

contract A {
    address public addressB;
    address public sender;
    uint public myVar;

    function A() {
        addressB = new B();
    }

    function makeCall(){
        addressB.call(bytes4(sha3('set(uint256)')), 1);
    }
    function makeCallCode(){
        addressB.callcode(bytes4(sha3('set(uint256)')), 2);
    }
    function makeDelegateCall(){
        addressB.delegatecall(bytes4(sha3('set(uint256)')), 3);
    }

    function reset(){
        sender = 0;
        myVar = 0;
        B(addressB).reset();
    }
}

contract B {
    address public sender;
    uint public myVar;

    function set(uint x){
        myVar = x;
        sender = msg.sender;
    }
    function reset(){
        sender = 0;
        myVar = 0;
    }
}