Unable to add .NET User Account in IIS 7.0

 Hi,
 
I am unable to add a user account in IIS 7.0 Manager.
 
The following error is occurring while trying to ".NET Users-->Add User.."
"The specifed password is Invalid.Type New Password"
 
Note:
1.I typed value in "Confirm Password" as same as "Password"
2.I logged in my admin account only
 
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