Problem Changing Windows Passwords

Problem Changing Windows Passwords

I seem to be having an unknown problem changing the administrator password on windows 2008 remotely. The password change fails in PMP with:

Activity logs : 
1. Access is denied. 

Trying to use Agent Mode : 
1. Agent not installed in xxx.xxx.xxx.



On the windows server side in the event viewer two events are generated.  Event ID 4776, and Event ID 4625 (logon type 3....network). The former would indicate the username is correct but the password is wrong. Verifying the password via PMP succeeds and logging in via RDP with that password also succeeds, so the password is definitely correct. The admin user is not denied access to the server from the network in the local security policy. 
Any ideas where I should look next 

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