Hallvardeb
I am sorry you're having trouble syncing your Forerunner 910XT. The ANT Agent was replaced so we would have one program that handles most of our devices instead of a different one for each type of device. I am sorry that it is not working in your situation. To help correct this, please try the steps in the FAQ, "">What can I try when my ANT Fitness device will not sync with Garmin Express?">What can I try when my ANT Fitness device will not sync with Garmin Express?"
It is also a good idea to delete Activities from your Forerunner 910XT periodically after they have successfully uploaded. Clearing this data will help prevent the device from getting full and causing corrupt data. Please see page 30 of the ">Owner's Manual">Owner's Manual to do this.
Let us know if you have more trouble.
Dave