A DESCRIPTION OF THE REQUEST :
Note: I am not very sure about the Solaris version.

The sun.security.krb5.internal.tools.Kinit class is missing from rt.jar. Infact the entire tools package is not included in the rt.jar. This is missing in JDK6 installation (jdk1.6.0_13 and onwards I guess).
The class is present in rt.jar which comes for JDK5 on the same environment.

However, on windows, the class is present both in JDK 5 and JDK6.

JUSTIFICATION :
If a program which uses Kinit.class is executed on windows, it works fine both on JDK5 and 6. However, on Solaris, it runs on JDK5 but gives classnotfound if executed on JDK6.