Have you switched away from the 8X permanently, or are you just using the Lumia for testing? I remember you writing that the 8X was the very best WP8 device.
I'd say that's more of a general OS problem, probably due to the strict limits on what an app can do when inactive. I wish the built-in Messenger would work reliably, at least. But alas, no.
If you're like me and you like to keep your context menu tidy, here's the key that needs to be removed from the registry to disable the useless Skydrive Pro entry: HKEY_CLASSES_ROOT\...
Have you tried using compatibility mode on the file?
You can use the rebate upgrade to do a clean install, too! Just use compatibility mode on the installation files. You can even upgrade from a pirated OS!