Are you using -1 (no response) as a valid response option? Using -1 as a correct response (so first, as in: -1,57) should have the resulting data list those nonresponses as TRUE.
If you want to send along your input file, I can take a look. Otherwise, you can compare your input file to one of the samples that capitalizes on having no reposne being vaild- the Go-No Go task (gnat). Compare your time file to theirs, and see if you can spot the difference.
Hope this helps!