Is the original poster's receive address 1s8Y - it seems so, if that address is labeled as a "receive from slush" address? If so, then this transaction quoted was not receiving coins, this transaction emptied the address.
In block 166289
, 0.5BTC (x5) is sent from 1s8Y7Bv1UkvLHk2B5JLW2tzXPhenC16AS
, with change going to 1s8Y7Bv1UkvLHk2B5JLW2tzXPhenC16AS. The odd thing is a smaller amount being sent five times in the same transaction from the same address.
It is not sent in a normal way, it is sent in several smaller transactions. Why? Likely because it is under control of the receiving address. The receiving address has received many other odd transactions with multiple inputs from the same address.
The receiving address also has received money from a vanity address 1BountYypWttTvAJcMJVvSRDfX3TJ182To. If we search, we can see that address is used in a tutorial on the strongcoin site for creating offline transactions
, in fact that bounty address belongs to forum user strongcoin developer dogisland.
So money was sent in a very strange way out of 1s8Y7, such as someone experimenting with or flooding offline transactions would do, to an address that has also received coins used in an offline transaction generator demo. Probably the original transaction as sent to the network had .5BTC being spent hundreds of times to make sure the wallet was completely tapped out. It is the extra spends in the transaction (the one sent between nodes, not the one included in the blockchain) that the client received that are still unconfirmed.