This has been going on for a couple of weeks.

I'll hover over "community" and the menu does not appear. Clicking on "community" brings me to the community hub. What it doesn't do is let me choose "discussions," though a few clicks through will eventually get me there.

At the same time, the Steam menu (upper row) stops responding to clicks, so I can't close Steam.

If I force Steam closed, for example by right-clicking on the system tray icon for Steam and selecting "exit Steam," and then re-start Steam, the problem goes away. For a few hours, at least.