I have a contract which I'd like to be able to sum numbers submitted by any other address:

    contract UnitCounter {
        mapping (address => uint256) public UnitsFrom;
        uint256 public TotalUnits;
    
        function submitUnits(uint256 Units) {
            UnitsFrom[msg.sender] = Units;
            TotalUnits += Units;
        }
    }


Using [this][1] a rough guidance, I followed the following steps on a private-net:

1. Deploy the contract using mist
2. Get the JSON Interface code using the "Show Interface" icon in mist
3. Copy the address of the deployed contract `0x17d541b8aACFFe473e3dD32eBA83C82B51DB8EF9` on my private blockchain.
4. On a Geth console:

    

    `var abi=[ { "constant": false, "inputs": [ { "name": "Units", "type": "uint256" } ], "name": "submitUnits", "outputs": [], "type": "function" }, { "constant": true, "inputs": [], "name": "TotalUnits", "outputs": [ { "name": "", "type": "uint256" } ], "type": "function" }, { "constant": true, "inputs": [ { "name": "", "type": "address" } ], "name": "UnitsFrom", "outputs": [ { "name": "", "type": "uint256", "value": "0" } ], "type": "function" } ]`
    
    `var MyContract = web3.eth.contract(abi);`

    `var myContractInstance = MyContract.at('0x17d541b8aACFFe473e3dD32eBA83C82B51DB8EF9');`

    `MyContractInstance.submitUnits('10');`

I then get the following errors:

    Error: invalid address
        at web3.js:3887:15
        at web3.js:3713:20
        at web3.js:4939:28
        at map (<native code>)
        at web3.js:4938:12
        at web3.js:4964:18
        at web3.js:4989:23
        at web3.js:4055:16
        at apply (<native code>)
        at web3.js:4141:16

**What do these errors mean?**

**How should I debug from this point?**



  [1]: https://github.com/ethereum/wiki/wiki/JavaScript-API#example-50