Hello and welcome.
Did you happen to modify any services?
What does the tool tip say when you place it over the icon?
Have you right-clicked on the icon and chosen Diagnose and Repair?
Have you installed any new software?
Thanks for responding.
The tool tip says "no internet access" but I do have access.
Diagnose and repair finds nothing wrong - presumably because nothing is wrong.
The only new software I installed is a backup program (Memeo) bundled with my WD external drive.
Resetting my FIOS router seems to have solved the problem.
Thanks to reghakr, Master Chief and Kevin for your help