Assuming a ERC-20 is deployed with the standard code from the website, why am I able to transfer tokens from the main address to any other ETH address with no issues, but when I send the tokens from that address to any other Ethereum address, calling "Function: transfer(address _to, uint256 _value) ***"

it gives the following message in Etherscan:

"Warning! Error encountered during contract execution [Bad instruction]"

What does this mean and how to fix this? Does the approve() function need to be called for every address before it can spend the tokens and can that approve function be called from the new address or must it be only from the original token creator address?

pragma solidity ^0.4.13;

contract tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData); }

contract Test {
/* Public variables of the token */
string public name;
string public symbol;
uint8 public decimals;
uint256 public totalSupply;

/* This creates an array with all balances */
mapping (address => uint256) public balanceOf;
mapping (address => mapping (address => uint256)) public allowance;

/* This generates a public event on the blockchain that will notify clients */
event Transfer(address indexed from, address indexed to, uint256 value);

/* This notifies clients about the amount burnt */
event Burn(address indexed from, uint256 value);

/* Initializes contract with initial supply tokens to the creator of the contract */
function Test(
uint256 initialSupply,
string tokenName,
uint8 decimalUnits,
string tokenSymbol
) {
balanceOf[msg.sender] = initialSupply; // Give the creator all initial tokens
totalSupply = initialSupply; // Update total supply
name = tokenName; // Set the name for display purposes
symbol = tokenSymbol; // Set the symbol for display purposes
decimals = decimalUnits; // Amount of decimals for display purposes
}

/* Internal transfer, only can be called by this contract */
function _transfer(address _from, address _to, uint _value) internal {
require (_to != 0x0); // Prevent transfer to 0x0 address. Use burn() instead
require (balanceOf[_from] > _value); // Check if the sender has enough
require (balanceOf[_to] + _value > balanceOf[_to]); // Check for overflows
balanceOf[_from] -= _value; // Subtract from the sender
balanceOf[_to] += _value; // Add the same to the recipient
Transfer(_from, _to, _value);
}

/// @notice Send `_value` tokens to `_to` from your account
/// @param _to The address of the recipient
/// @param _value the amount to send
function transfer(address _to, uint256 _value) {
_transfer(msg.sender, _to, _value);
}

/// @notice Send `_value` tokens to `_to` in behalf of `_from`
/// @param _from The address of the sender
/// @param _to The address of the recipient
/// @param _value the amount to send
function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
require (_value < allowance[_from][msg.sender]); // Check allowance
allowance[_from][msg.sender] -= _value;
_transfer(_from, _to, _value);
return true;
}

/// @notice Allows `_spender` to spend no more than `_value` tokens in your behalf
/// @param _spender The address authorized to spend
/// @param _value the max amount they can spend
function approve(address _spender, uint256 _value)
returns (bool success) {
allowance[msg.sender][_spender] = _value;
return true;
}

/// @notice Allows `_spender` to spend no more than `_value` tokens in your behalf, and then ping the contract about it
/// @param _spender The address authorized to spend
/// @param _value the max amount they can spend
/// @param _extraData some extra information to send to the approved contract
function approveAndCall(address _spender, uint256 _value, bytes _extraData)
returns (bool success) {
tokenRecipient spender = tokenRecipient(_spender);
if (approve(_spender, _value)) {
spender.receiveApproval(msg.sender, _value, this, _extraData);
return true;
}
}

/// @notice Remove `_value` tokens from the system irreversibly
/// @param _value the amount of money to burn
function burn(uint256 _value) returns (bool success) {
require (balanceOf[msg.sender] > _value); // Check if the sender has enough
balanceOf[msg.sender] -= _value; // Subtract from the sender
totalSupply -= _value; // Updates totalSupply
Burn(msg.sender, _value);
return true;
}

function burnFrom(address _from, uint256 _value) returns (bool success) {
require(balanceOf[_from] >= _value); // Check if the targeted balance is enough
require(_value <= allowance[_from][msg.sender]); // Check allowance
balanceOf[_from] -= _value; // Subtract from the targeted balance
allowance[_from][msg.sender] -= _value; // Subtract from the sender's allowance
totalSupply -= _value; // Update totalSupply
Burn(_from, _value);
return true;
}
}

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