Unable to download purchased content in Marketplace

Am able to access / browse Marketplace fine - including purchasing new content.

However, am unable to download any content in my library - new or old. Attempting to download content takes me to the downloading screen, but it hangs at 0%.

After about 15 minutes of waiting, I gave up and attempted to cancel the download. Now the package says it's perpetually trying to download. Rebooting my machine, logging in / out did nothing.