itunes movies wont download

i have some tv shows that are bought on itunes, and some that are downloaded from websites other than itunes. I downloaded alot from both locations, however some videos will not load on to my ipod touch 3g. these are just random videos. on my ipod touch, i get an alert saying: this item could not be synced. see itunes for more info, and the episode shows up faded on my ipod in movies. I cannot open the episode on my ipod either. can anyone help PLEASE PLEASE PLEASE!!!