ReferenceError: Error #1065: Variable is not defined

Good people of Kirupa.
Please help me out with this error message.
No matter how simple my class is Flash gives me this error message :
“ReferenceError: Error #1065: Variable is not defined.”

In fact, it happens even if I don’ have any variables at all. It won’t even run a simple “hello world” trace from the constructor method.

From what I’ve learned from other people, this could often be caused by not declaring your classes public, but I have that.

Any ideas on what causes this?