What URL is this happening at?
How many "create_account.php" files do you have under your /includes/languages/ area?
If you search for "EMAIL_GREET_NONE" using the Developers Toolkit, where do you find it defined? (searching ALL files in Catalog)
Do another search for ALL Catalog files for EMAIL_DISCLAIMER_NEW_CUSTOMER. Where do you find it?

What version of Zen Cart?
What addons/contributions do you have installed?

You said you did a compare of files ... which files did you compare? Did you compare *everything* or just a few language files?