[Ethereum] How to explore all transactions for a given account

If I understand your question correctly you want to be able to see who has deposited Eth to your contract address. This is what event logs are for.

(1) Create a contract where there is an event every time there is a transaction. e.g something like:

contract someContract {   

    address public owner;

    // Set the owner of the contract to be the creator of the contract i.e. you
    function someContract() {
        owner = msg.sender;
    } 

    // This is an event 
    event DepositMade(address _from, uint value);
    event WithdrawalMade(address _to, uint value);

    //Catch all function 
    function() {
        // generate an event when someone sends you Eth
        if (msg.value > 0)
            DepositMade(msg.sender, msg.value);
    }

    // Only the owner of the site can withdraw Eth
    modifier admin { if (msg.sender == owner) _ }

    function withdraw(uint amount, address recipient) admin {
        if(recipient.send(amount))
            WithdrawalMade(msg.sender, msg.value);
        else throw;
    }
}

The important bits are defining an event type event DepositMade(address _from, uint value) and generating an event when something happens DepositMade(msg.sender, msg.value);these events are stored in the event log associated with the address of the deployed contract instance.

(2) You retrieve the events on this contract using rpc eth_newFilter or web3.eth.filter e.g something like:

var filter = web3.eth.filter({fromBlock:0, toBlock: 'latest', address: contractAddress, 'topics':['0x' + web3.sha3('DepositMade(hexstring,uint256)')]});
filter.watch(function(error, result) {
   if(!error) console.log(result);
})

We were getting the same error and it turned out that there were two conflicting keyfiles. One in the default (~/.ethereum) and one in a custom location that we had specified using --datadir.

In the end it was just a case of cleaning up the scripts we were using to deploy the geth node to make sure that we consistently only used one or the other keystore (we went with the default in our case)

Once we had done that, the problem was solved.