I select to download a part of a torrent e.g. 2 out of 15 songs and ktorrent says download finished and torrent goes to seeding mode.I can hear all songs perfectly so download is indeed finished.But sometimes if i restart ktorent then (only the partially donwloaded torrents) return to download mode again and ktorrent downloads some MB's again.After that download finished again etc....

Im using ktorrent 2.2.5 shipped with kubuntu.

Is this a bug fixed on later releases?

Yes, try 2.2.7 or 3.1.1

2.2.7 is probably in the repo's if you enable the backports of kubuntu.

its not at the ubuntu backports,but i found some ubuntu deb packages on for ktorretn 2.2.7,so im ok.
Thnx for your help