http://ethereum.stackexchange.com/questions/6975/type-inaccessible-dynamic-type-is-not-implicitly-convertible/7546?noredirect=1#comment7412_7546

dynamic-type-error.sol

contract A {
  A other;
  function Assign(address a) {
      other = A(a);
  }
  function Get() constant returns(bytes8[]) {
    bytes8[] stuff;
    return stuff;
  }
  function Copy() {
    bytes8[] memory stuff = other.Get();
  }
}

contract Test {
    function Test() {
        A one = new A();
        A two = new A();
        one.Assign(address(two));
    }
}