I too have been getting this error when attempting to convert a newly purchased song to mp3. This has only started happnning recently in iTunes 10.6.3.25. It turns out that this happens when the newly purchased songs are not complete. The real problem seems to be with downloading new songs form iTunes Store. iTunes reports a successful and complete download, but when I go to play the song, only 30 seconds to a minute of audio exist. It has been occurring so frequently, that I will not purchase another song until the problem is fixed. I tried redownloading an album 5 times already, one song at a time while checking each song in between with no success. Anyone at Apple know what's wrong with their software?