Q: an unknown error has occurred (-50)

Try here >  iTunes Store: "Error (-50)" when downloading purchased content

I am having this same problem, too. I connect, download 20-50MB, then the download stops and I get the -50 error. I've portforwarded, my MBP firewall is off, checked that my DNS isn't through Google, reset parental controls, disabled sources in iTunes, etc. I was able to download two episodes of Sons of Anarchy, but it has been sporadic. One episode I downloaded finished, reset, then started over. I have 5megabit download and 0.5megabit upload; I've turned off all other programs, no one's gaming, and I'm still having problems.

Your connection speed and quality is determined by the poorest link between your hard drive and Apple's.

Thanks for replying, but when I'm able to download a 1GB file in less than an hour from elsewhere on the same computer, I don't understand what that means.