SQL Server 2008 R2 Install ?

I'm halfway through the prep steps for this install, and when I specify one or more service accounts and passwords, I always get "The credentials you provided for the blah blah blah service are invalid..." I'm doing this pretty much the same way I set up our old SQL 2005 machine - one (domain) account for all services, because there's only one app that hits the DB and it's local to the machine. I'm browsing for the account in AD, and entering the correct password. Any ideas?