I'll be honest here. I highly doubt you'll get a refund, regardless of the issues. This is one area that I am incredibly disappointed in with Xbox streaming.
I had issues with a streaming video once. Purchased it, and went to the Xbox. Xbox said that it was past the "14 days" even though I downloaded it no more than a minute ago. Contacted support within the hour and they couldn't refund it because "this is a non refundable purchase." Even after explaining the situation to a T, they eventually just added the movie back into my account to let me rewatch it... even though I had already went out and rented it physically. Awesome.
Its worth a try, but I am skeptical. Let me know what happens for you, because this was one of the most frustrating things with Xbox this past year.
EDIT: Even in this case, I'm not sure who to contact. Since it was purchase through Xbox, I'd assume them. 1-800-4-MY-Xbox in the US.