domain user account get locked after every few minutes
I am administering a windows domain having windows Server 2003R2.
i make a group policy that after three wrong attempts of password.user account will get locked for 15 minutes.
now i am facing a problem that when i logon to any User's PC with adminstrator credential and then log off.then i trying to login with user's credential.it showing me that user account is locked out.
it is not neccessary that after logging off by administrator's credential on user PC.User account get locked.it also get locked every after 5,6 minutes.
sometime when user is already logged in.he is facing a problem that he cannot use print services.
when i checked out his account in Active directory.it showing me locked.
is this any kind of virus/malware.or some configuration error.kindly advice me what i do to resolve that matter
i also tried fixdownadup.exe on all PC but still accounts get locked rapidly.Plzzzzzzz advise me