Locked accounts

I have a win 2000 Active directory… I also have some users trying to log into it getting account is locked error. However when I look at the clients account details show the account is not locked… I’ve waited a few hours, incase it’s a replication issue, but some of these users still cannot log in. I’ve even deleted and re-created there accounts, but still no luck… Any ideas what could be causing this?
Clients are using XP Pro