Are they recent purchases or tracks that have become corrupted since you downloaded them. Depending upon what country that you are in (music can't be re-downloaded in all countries) then try deleting the incomplete tracks from your iTunes library and redownload it via the Purchased link under Quick Links on the right-hand side of the iTunes store home page on your computer's iTunes : re-downloading.
If you aren't in a country where you can re-download music or if they re-download in the same state then try the 'report a problem' link from your purchase history : log into your account on your computer's iTunes via Store > View My Account (Store > View My Apple ID on iTunes 11) and you should then see a Purchase History section with a 'see all' link to the right of it ; click on that and you should see a list of your purchases ; find those songs and use the 'Report a Problem' link and fill in details about the problem (iTunes support should reply within, I think, 24 to 48 hours).
Some people have had a problem with the 'report a problem' link (it's been taking people to this site on a browser instead of showing a form in iTunes) - if it does that to you then 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.
They have been this way since download. They are recent purchases (this month) and i am located in the US so it shouldn't be an issue. I did delete them from the itunes library, but since they are on the ipod, the application wants to move them from the ipod or delete from library, which i suspect is what you are suggesting, since just deleting them from the itunes library didn't seem to make a difference. I went to the itunes store>purchased and they show up there, but they aren't available for download (its greyed out)
As you've marked your reply as having solved the question I'm not sure whether you still have a problem or not.
You should be able to delete a song from your computer's iTunes library, re-download it via the Purchased link on the store's home page, and then re-sync it to your device (or delete it from the device as well and then sync).