problems converting song from AAC to MP3 in iTunes

hi,

I have just downloaded some songs from the iTunes store and they download in the AAC format, I usually right hand click on a song and convert it to MP3 file, however I have one song "animal by neon trees" that it keeps coming up with an error but it says it is an unknown error. this is what it says

error occured while converting the file "animal". an unknown error occurred (-3)

has anyone else encountered this issue??

please help

ps. i have the latest version of itunes, i have also converted other songs today not a problem.