Question Concerning Kerberos "Additional Pre-Authorization Required" Error

[Ed Brown]

Hello,
I'm getting the following error when I tried to authenticate using Kerberos 
from Apache DS Studio:

[15:27:55] DEBUG [org.apache.directory.shared.kerberos.messages.KrbError] - 
KrbError initial value :
KRB-ERROR : {
    pvno: 5
    msgType: KRB_ERROR
    sTime: 20150608192755Z
    susec: 0
    errorCode: Additional pre-authentication required
    realm: EDWIN.COM
    sName: { name-type: KRB_NT_SRV_INST, name-string : <'krbtgt', 
'mytest.com'>realm: MYTEST.COM }
    eText: Additional pre-authentication required



What is causing this to happen and how do I fix it?
I followed the instructions in the manual, multiple times.

Thanks in advance.

Ed Brown