Well, what if I tried to download a music video I just purchased, and it "fully" downloads, but really only half-way downloads?

My internet is terrible, and must have lagged in the downloading of a music video I purchased. It says it fully downloaded, but would only play music and video half way through, and freeze, yet the timer still played. I cannot re-download it, as it says I already have.

I've tried deleting itm and re-downloading it, but I cannot, as I "already have it".

What do I do? I gave money, and recieved nothing in return.