The tabbed navigation on a team site was highlighting a tab when not on that page. For example, when on the home page, the tab for a sub-site was highlighted.
The problem was in the URLs for the navigation. Some of them had sites/mysite/default.aspx and some of them had sites/mysite/ as the URL. To resolve the issue, make them all uniform. For example, change them all to /default.aspx or take the default.aspx off of all of them.
This solution was found here: