Downloads from SkyDrive broken
In a recent change to its SkyDrive service, Microsoft have introduced a bug that causes corruption of files downloaded by older or existing apps (including Account Tracker for Windows Phone). See http://architects.dzone.com/articles/skydrive-breaking-changes-live.
I reported this to Microsoft a couple of days ago, and they were unaware of the issue. They are now investigating. I am hoping they can fix this at their end, rather than it requiring an app update.
Note that existing backup files are actually fine, and should be useable again once they fix the download problem.
UPDATE 1 (29th July) – I am about to submit a fix for this to Microsoft.
UPDATE 2 (2nd August) – Microsoft have now fixed this. See http://social.msdn.microsoft.com/Forums/live/en-US/52ab9b0f-71f5-437e-be0b-48115a9ba0a9/skydrive-update-related-to-sdk-5052-and-wlupload.