FULL PRODUCT VERSION :
java version "1.6.0_10"
Java(TM) SE Runtime Environment (build 1.6.0_10-b33)
Java HotSpot(TM) Client VM (build 11.0-b15, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.0.6001]

A DESCRIPTION OF THE PROBLEM :
In jdk/lib/ct.sym are not all classes from rt.jar.
For example com.sun.xml.internal.bind.marshaller.NamespacePrefixMapper is missing.
So it is not possible to compile a class depending on such class.

Example:

/////////////Java-File Start
package gbo.test;

import com.sun.xml.internal.bind.marshaller.NamespacePrefixMapper;

public class NamespacePrefixTest extends NamespacePrefixMapper
{

    @Override
    public String getPreferredPrefix(String arg0, String arg1, boolean arg2)
    {
        return "test";
    }
}
/////////////Java-File End

Compiler:
D:\dev\src\gbo\test>javac NamespacePrefixTest.java
NamespacePrefixTest.java:3: package com.sun.xml.internal.bind.marshaller does not exist
import com.sun.xml.internal.bind.marshaller.NamespacePrefixMapper;
                                           ^
NamespacePrefixTest.java:5: cannot find symbol
symbol: class NamespacePrefixMapper
public class NamespacePrefixTest extends NamespacePrefixMapper
                                         ^
NamespacePrefixTest.java:8: method does not override or implement a method from a supertype
    @Override
    ^
3 errors

Compiling in NetBeans produces the same error.
Compiling in Eclipse works.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
it should compile without error.

REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
delete jdk/lib/ct.sym or
use Eclipse compiler