you are setting zero fees to the client but it sends a fee without telling you.
I don't know of any versions that did that.
The most recent version (v0.3.24) will pop up a dialog box that says the transaction fee is required and will display the amount.
its not only the fact that there is no FAQ
Added.
-
http://en.bitcoin.it/wiki/FAQ#How_much_will_the_transaction_fee_be.3FPlease know that the client cannot say something like: the fee for getting this transaction processed in the next block is N bitcoins.
That is because there is no set fee. When the client comes up with a number, it is only making an estimate. It is up to the miner to determine whether or not to include a transaction. The higher the fee, the more likely the transaction will get included. Even a high fee though is not a guarantee.
Currently, the 50 BTC reward is adequate for many miners so that is why you will see transactions with no fee in many of the blocks yet.