It seems that you are concerned about funds from a transaction that was sent to you after a backup of your private keys has been made. That's not something to be concerned about.
The private key is only needed to spend any bitcoins sent to your Bitcoin addresses. When you have imported the private key, all unspent transactions to that private key's corresponding Bitcoin address can then be spent, regardless of when those transactions occurred (i.e., including transactions that were sent after your backup was made).
Now keep in mind that if you are the sender of a payment, change goes to a new bitcoin address in your wallet. A backup will contain a number of addresses (default is 100) in a key pool which are used for transactions that follow when you made your backup, however if you are frequently sending funds you should frequently be making additional backups.
You generated some addresses without the Bitcoin client and you want to know if the Bitcoin Client will show any incoming payments directed to any of these, is that correct? – cdecker – 2013-07-31T09:20:46.133
Yes :) I generate the addresss with the same private key as i use in the Client. – imises – 2013-07-31T12:40:26.757
How did you generate the 1.000 addresses from the one (???) private key? – cdecker – 2013-08-01T13:25:04.550
That was my mistake: i thought private key and address(s) where 1:n, but its 1:1. – imises – 2013-08-01T13:34:23.717