Have you installed pykerberos?
Also, use klist to check that the tgt ticket is for the user and domain you expect.
be aware that the domain name seems to need to be in upper case so
kinit
us...@MY.DOMAIN.COMnot
kinit
us...@my.domain.comAlso, make sure you have patched windows server 2008 R2 - as per this advice on
http://docs.ansible.com/intro_windows.html#windows-system-prep"On Windows 7 and Server 2008 R2 machines, due to a bug in Windows
Management Framework 3.0, it may be necessary to install this
hotfix
http://support.microsoft.com/kb/2842230 to avoid receiving
out of memory and stack overflow exceptions. Newly-installed Server 2008
R2 systems which are not fully up to date with windows updates are known
to have this issue."
I recommend running your ansible-playbook -vvvvv to see the connection debugging information if it still fails.
Also running eventvwr on the windows machine and checking if there are any logon events in Windows Logs -> Security
Hope this helps.
If you discover anything that helps please reply so we can provide more information in the documentation.
Jon