Weird SBS Password Policy Behavior

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I've set a GPO at the domain level to implement a password policy. The policy
is as follows:

enforce passwd history: 3
maximum password age: 90
minimum password age: 0
minimum passwd lenght: 8
passwd must meet complexity requirements: Enabled

Now, when a user tried to change his passwd with ctrl+alt+canc he always
gets that his password doesn't meet complexity requirements even if it does.
The weird thing is that if i try to set it from the Users and Computer
Snap-In it accepts the password because IT DOES meet complexity requirements.

I've implemented password policies tons of times on std servers and never
experienced such a problem.

Anyone can help?
.