Problem transferring song(s)

My boys have iPod Touches and while trying to transfer some new songs onto them, I noticed that one song won't transfer. I thought maybe it was due to me having restrictions on the Touch and the song claimed to be "Explicit", however I changed their settings and the song still won't transfer.

The song plays on my Mac and also on my Nano.

I'm not sure what the problem could be. Any ideas? Would erasing all data on the Touch and starting over help?

Have you looked at the info for the track? It may be locked>
Highlight the offending item, and in the file menu select get info.

Ok, I checked the info and it says "protected AAC audio file". I checked my Purchase history and I did indeed buy this song. Why am I having this problem?

I also looked in the store and the song no longer has the "explicit" tag on it.

I bought it again and it transfered. But any reason/idea why I ran into this in the first place?

Sorry for the delay in replying again.
No reason comes to mind, especially as it worked after buying it again.
I wonder if something got altered when you were moving it around/attempting to transfer before.