unknown error 12004

I downloaded 2 movies for my kids to put onto my iPhone4 for a trip we are taking tomorrow. I tried downloading it onto my old iPhone3 but it said I already had it downloaded someother place. So I thought maybe I cannot download movies to that old phone as I cannot rent tv shows on it either.

Never had a problem downloading tv shows or rented movies to my iPhone4. What is the error? I have not downloaded it onto any other device. Just onto my iMac OS X

I have the iPad2, iTV but have not attemted to downoad to those items as I want the movies on my iPhone.

Thanks