Consider the following test case, with a bogus symbol in it:

import javax.swing.*;

public class MesgTest{
    public static void main(String[] args) {
        JButton b = new JButton();
        b.setSelected(BOGUS);
    }
}

When I compile it under 1.4.2 I get 1 error message (as expected):
MesgTest.java:6: cannot resolve symbol
symbol : variable BOGUS
location: class MesgTest
        b.setSelected(BOGUS);
                      ^
1 error

When I compile it under 1.5.0 I get the following 2 errors:

MesgTest.java:6: cannot find symbol
symbol : variable BOGUS
location: class MesgTest
        b.setSelected(BOGUS);
                      ^
MesgTest.java:6: internal error; cannot instantiate setSelected(boolean) at java
x.swing.JButton to (BOGUS)
        b.setSelected(BOGUS);
         ^
2 errors

The second error message makes absolutely no sense to me, and I believe it will cause confusion.

I have inquired about this to a couple of people, and a response from ###@###.### indicates that this is a bug.