Did you say you tried to click "Back to Game" but instead placing and breaking blocks?
Anyway, this input handling issue is a long known bug of Minecraft for Linux.
The first thing you should try is running Minecraft with Java 6. Many claimed that Minecraft works better in JRE 6, hopefully this is a solution for you.
If the above doesn't work, please download, extract and replace your lwjgl file. You can download it here.
Supposing that you know how to use Linux, please try to run this command in terminal and tell us the output(This is a test of your PC's graphic support, not going to download/install anything):