If using Internet Explorer, check to see if garmin.com is in your trusted sites.
If so, try either:
remove it
or
make sure that the box for "require server verification (https: ) for all sites in this zone" is unchecked.
The urls for these forums are https ......... the urls for garmin connect are http ......... so having garmin.com in trusted sites and having that box checked would allow access to the forums but deny garmin connect.
