Can not compile enums in Eclipse

While trying to introduce enums in my Android project in Eclipse, I encountered with the following problem: Compiler says:

1. The type java.lang.Enum cannot be resolved. It is indirectly referenced from required .class files
2. The type Enum is not generic; it cannot be parameterized with arguments

I work under Ubuntu 10.04 and use Eclipse v.3.5.2. Tried to use both Java 6 OpenJDK and Java 6 Sun, but without success.

Can anybody help me to sort out with this issue?

Here is the code:

public class MyClass {

  public MyClass() {
  }

  ...

  enum MyEnum {
    CONST1, CONST2, CONST3;
  }
}