I wrote at some point in the past about a small bug in Gnome 3 where Netbeans menus behaved strangely. My solution then was to switch to Gnome classic. Well I started using Cinnamon recently and found that it has the same issue. So I wanted to find a better solution.
I came across a strange way to fix the issue. I tried it out, and it worked beautifully, even if it is weird.
Unmaximize Netbeans so that it is in a Window on the desktop. Grab the top left corner of the Window and move it all the way to the top left side of the screen. Now, maximize it. The menus work again.
It's weird, but I'm glad it works. I spend most of my time in Netbeans, and I'm really digging Cinnamon.