Solve iTunes Error 50
If you suspect a program is causing the problem, close your Internet browser and any other applications that use the Internet except for iTunes. Close the suspected application, such as your anti-virus or firewall. Try re-downloading your content. If you do not receive the iTunes Error 50 message, the program you closed is more than likely the cause.
You can fix this error by adding an exception to your application's list. Consult the Help section of the suspected software for the exact steps on adding exceptions. The following addresses or domains need to be added to the exceptions list in order for the iTunes store to send and receive data:
If you cannot add exceptions to your program, the easiest way to solve the problem is by closing the program before downloading content from iTunes. You can restart the program as soon as the downloads are complete. To keep your system safer with a firewall or anti-virus program closed, do not browse the Internet while these programs are closed or stopped.
To delete cached video files, navigate to the following folder:
Mac Systems: /Music/iTunes/iTunes Media/Downloads
Windows Systems: \Users\username\My Music\iTunes\iTunes Media\Downloads\
Open the folder containing your video downloads. Delete the file ending in tmp. Open iTunes and try to re-download the video.