Have the same amongst a million other issues I've noted all over this poxy website. I've checked the folders on the computer and there is no pending workouts to be transferred to connect so where it's sending this data I have no idea. It's not to Garmin Connect.
Tried to just sync my 910XT with an activity from today, but doesn't seem to work. The watch shows "Transferring Data", but the Last Sync date on Express doesn't change, and there's nothing showing up on GC