I am working on truffle and running these codes to run an example:
truffle(development)> var hw  
undefined 
truffle(development)> HelloWorld.deployed().then(function(deployed){hw=deployed;}); 
undefined 
truffle(development)> hw.SayHello.call() 
I am getting the following error:
***Error: VM Exception while processing transaction: revert 
    at Object.InvalidResponse (C:\Users\dell\AppData\Roaming\npm\node_modules\truffle\build\cli.bundled.js:41484:16) 
    at C:\Users\dell\AppData\Roaming\npm\node_modules\truffle\build\cli.bundled.js:328866:36 
    at C:\Users\dell\AppData\Roaming\npm\node_modules\truffle\build\cli.bundled.js:324536:9 
    at XMLHttpRequest.request.onreadystatechange (C:\Users\dell\AppData\Roaming\npm\node_modules\truffle\build\cli.bundled.js:327565:7) 
    at XMLHttpRequestEventTarget.dispatchEvent (C:\Users\dell\AppData\Roaming\npm\node_modules\truffle\build\cli.bundled.js:176407:18)  
    at XMLHttpRequest._setReadyState (C:\Users\dell\AppData\Roaming\npm\node_modules\truffle\build\cli.bundled.js:176697:12) 
    at XMLHttpRequest._onHttpResponseEnd (C:\Users\dell\AppData\Roaming\npm\node_modules\truffle\build\cli.bundled.js:176852:12) 
    at IncomingMessage.<anonymous> (C:\Users\dell\AppData\Roaming\npm\node_modules\truffle\build\cli.bundled.js:176812:24) 
    at emitNone (events.js:111:20) 
    at IncomingMessage.emit (events.js:208:7) ***
My code is as follows:
HelloWorld.sol 
        pragma solidity ^0.4.8;
contract HelloWorld { 
   function SayHello() public returns (string) { 
        return ("SomeHello"); 
    } 
} 
2_deploy_contracts.js 
var ConvertLib = artifacts.require("./ConvertLib.sol");
var MetaCoin = artifacts.require("./MetaCoin.sol");
var HelloWorld = artifacts.require("./HelloWorld.sol");
var second = artifacts.require("./second.sol");
module.exports = function(deployer) { 
  deployer.deploy(ConvertLib);
  deployer.link(ConvertLib, MetaCoin); 
  deployer.deploy(MetaCoin); 
  deployer.deploy(HelloWorld);
  deployer.deploy(second);
}; 
My truffle.js 
module.exports = { 
  networks: { 
    development: { 
      host: "localhost", 
      port: 8545, 
      network_id: "*" // Match any network id 
    } 
  } 
};
I am working on Ubuntu 14. How do I solve it?