your computer could not be joined to the domain because the following error has occured,access denied

your computer could not be joined to the domain because the following error has occured,access denied,
this error is happening when i create users for active directory users and computers in windows server 2003,i have 11 computers ,,1 server and 10 clients,,i created 10 users in active directory users and computers ,,until here i have no problem,,but when i want join client computers with server it is happening this error(your computer could not be joined to the domain because the following error has occurred,access denied)
i can join 3 client computer with the server in fourth computer it happening that error,,please what can i do?

I think that you will either have to change the name of your computer or get a domain admin to remove the existing computer account which has the name you want to use.