The following simple script for naming and saving a currently open TextEdit document works from AppleScript but fails under Automator.
set file_name to "Gotcha "
set c_date to (do shell script "date +%Y%m%d_%H.%M.%S")
set file_path to (path to desktop as string) & file_name & c_date & ".rtfd"
tell application "TextEdit"
close document 1 saving in file file_path
end tell