The storm has passed
Multiple networks going down and being manipulated? It’s a Christmas tradition at this point. In addition to the Steam issue yesterday Microsoft has been having problems for several days now, but thankfully, we’ve been given the all clear.
Microsoft has announced that you now should be able to download items and purchase them as normal. For the past week or so I’ve been having problems with apps as well (including Blu-Ray player updates, which foiled me from watching the Alastair Sim Christmas Carol, also known as Scrooge, for a bit), but now it seems to be fine.
Xbox Live Service Status [Microsoft]