Q: Some downloaded songs will not play all the way thru!

If you select the 'songs' view in the music part of your iTunes library (there should be a series of buttons across the top of the screen), does the 'time' of those tracks agree with their specified length in the store, and if you select a track and do 'get-info' (control-I) then the 'stop time' on the Options tab is the same as the length e.g. that 'stop time' isn't telling iTunes to stop playing it before the actual end of the track ?

If they are recent purchases, then depending upon what country that you are in (music can't be re-downloaded in all countries) then try deleting those tracks from your iTunes library and redownload the, via the Purchased link under Quicklinks on the right-hand side of the iTunes store home page on your computer's iTunes.

If you aren't in a country where you can re-download music or if they re-download with the same problem then try the 'report a problem' page to contact iTunes Support : http://reportaproblem.apple.com

If the 'report a problem' link doesn't work then you can try contacting iTunes support via this page : http://www.apple.com/support/itunes/contact/- click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption