lost connection to Basemaps and ArcGIS Online from Desktop

For the past week or two, I have been unable to add Basemaps from ArcGIS Online, from the Add Data button in ArcMap. See this screenshot-- when I click Add Basemap, the window giving me the choice of Imagery, Bing, Streets, etc. doesn't show; nothing happens. Also note that the Add Data from ArcGIS Online, which shows a similar window, is disabled.

I tried logging out and in to ArcGIS online, no good. Any idea what could be wrong?

Thanks,
Kenny

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