Eclipse 3.8.1 - Error: Could not find or load main class

Hello,

I have several java files (.java) that I compiled and executed all day on a computer at school ruing Eclipse on Windows. When I came back home, I created a new project in my computer (Xubuntu 14.01) in Eclipse and tried to compile/execute the project. I got the following error:

Error: Could not find or load main class app2.DescenteRecursive

I spent all night reading online about this error but no one seems to really know how to fix it. Does anyone have an idea why this is happening?

Note: I even tried building a small test project with only a main in a class and I got the same error...

java -version gives me this, so it is installed:

java version "1.8.0_91"
Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)