Download and update files corrupted

I have a strange problem. When I try to download files, about 80% of the time when I run them I get a corrupt file error. This is also occuring during system updates, though in some cases it eventually completes the update.

I have another desktop connected to my router that downloads with no problems and a laptop that connects by wireless that also downloads and updates without issue.

To make matters stranger, my Local Area Connection icon in the system tray is displaying more packets sent than received (almost 5 to 1).

The only thing I haven’t tryed is changing the Cat5 cable in case I installed a crossover on accident. Is that a possiblity or could this be something else?