you definitely do not have to create the computer account in UCS before joining; that's done automatically during the join process. The same applies to DNS records.
Judging from the results one gets when searching for your error message I'd first check the domain name you've entered in your Windows PC. First log in to the UCS server with SSH (or on its console) and enter the following two commands in order to retrieve the (short) domain name and the Kerberos realm/full domain name:
ucr get windows/domain
ucr get kerberos/realm
The value retrieved from "kerberos/realm" is the domain name you have to enter on the Windows side as the new domain name.
On my test server this is the result:
[0 root@master ~] ucr get kerberos/realm
[0 root@master ~] ucr get windows/domain
Next when prompted for credentials use "administrator" or "short-domainname\administrator" (this would be "MBU-TEST\administrator" in my example) as the user name with the password you've chosen during the installation of UCS.