We are aware of an issue that will result in loss of your last workout. The issue is affecting some users when they stop their workout and exit the application. You will see your workout before exiting the app but after you’ve closed the app and re-open it the workout is lost. It doesn’t happen all the time and it is not affecting everyone so you might not see it.
As a temporary measure to prevent any data loss, please make sure you sync your data to SkyDrive after completing a workout and before exiting the application. We are working on an emergency fix…..more to follow.