New answers tagged transparency
I'm a MATE user (under Linux Mint), and this issue was also window compositing for me. To turn it on in Mint 17/MATE, go to Menu -> Desktop Settings -> Windows, and check off the box that says "Use compositing", then restart mdm or reboot your machine.
It sounds like Lubuntu 14.04 is having some display issues and not working right... if you installed it now you'd probably still have the same problems. You should probably fix the display issues first (could try booting with some of the troubleshooting-type kernel options from the grub (Ubuntu) menu, under "F6 Other Options" like nomodeset, noapic, ...
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