Intermittently, when I left-click on the Applications/Places/System menus, the first click does nothing, and it takes a second click to drop the menu. I've also noticed that hiarchial menus sometimes don't show their expanded menus unless I move the mouse pointer away to another menu item, and then come back into the hiarchial menu. And lately, I've even noticed that in some applications, menus are acting the same way. Any ideas? Cheers, Al
Actually, Takkat and Tinhed have it right. It's compiz related. I discovered this by turning off all visual effects in the Appearance preferences, thereby disabling compiz. The problem went away.
Then I used Ubuntu Tweak to enable composting under Metacity, and the problem came back, only worse! Clue! So I re-enabled visual preferences, and then went back to Ubuntu Tweak and turned off composting in Metacity.
Then I went to CompizConfig Settings Manager, in the system/preferences menu, and changed these: 1) in General Options/Display Settings, changed the Refresh Rate from 50 to 60 (which matches the rate shown in the Monitors preferences, 2) then went to Utility/Workarounds and disabled the "Force sync between X and GLX".
And so far, it's working!!!
Oh, I forgot to mention that I re-enabled Visual Effects in the Appearance preferences so that compiz was running again.