One suggestion: If you keep getting failed downloads, you may want to be sure you've set your wi-fi not to shut off when the device is plugged in (otherwise, it may turn-off when the device "sleeps"). To do this, go to network settings, then press the menu button. A two-button menu will pop-up. Press "advanced". Press "Wi-Fi sleep policy" at the top of the screen. Select either "Never" or "Never when plugged in."

That might help.