Some claim to have found a workaround via the browser.
<quote>
downloaded and installed Netflix and then it asked me for my account payment details for any future purchases.
< /quote>
So, see if you can use IE to launch the Store by doing a search for whatever you are trying to download and appending site:apps.microsoft.com to your search expression. Presumably if you were downloading free apps you wouldn't have to do that much.
Good luck
Robert Aldwinckle