I'm also having this problem. I click the workouts tab and it takes me to the next page where I can click the 'create your first workout' button. When I click the button the page refreshes, and all I can see is the garmin page header, and the footers (help, garmin connect, garmin, getting started etc in light grey). There is nothing else on the page to click.
All other tabs work fine - I can edit activites, create goals etc etc. Just activities is not working.