Check the /includes/modules/payments directory ...
Do you have additional files in there that end in php that do not come with Zen Cart?
This includes any files you may have added or renamed ...
Check the /includes/languages/english/modules/payments directory ...
Also be sure that there is a matching file for each in the two directories ...
Then check that the files in the:
/includes/modules/payments
directory are the program files and not the language files ...
Then check that the files in the:
/includes/languages/english/modules/payments
directory are the language files and not the program files ...