Cannot login rsa@logserver ip address
You'll need to go into the Netwitness UI and click down into the log collector's configuration page like this one here.This shows the VMWare collections. See under Sources the two ESX servers. If you click on one and then the Edit button you'll see the next screen shot.
Under the Username and password this is what you have to make sure is correct for the ESX it is trying to pull logs from.