Example:

package test;

    package test;
    
    public interface Test {
        interface A {
            interface B {
                void g(A a);
            }
            
            void f(B b);
        }
    }

Applying "Move Inner to Outer Level" to A generates the following:

    package test;

    import test.Test.A.B;

    public interface A {
        public static interface B {
            void g(A a);
        }

        void f(B b);
    }

The import statement references the previous location of the nested class B that was moved with A, causing a compile 
error.

As a minor point, it's inconsistent that "public" is being added to "interface B" but not to f() and g().

Product Version: NetBeans IDE 6.1 Beta (Build 200803050202)
Java: 1.6.0_04; Java HotSpot(TM) Client VM 10.0-b19
System: Windows XP version 5.1 running on x86; Cp1252; en_US (nb)