Hello,
The value "1#INF" is often an indication that the payback period is greater than the analysis period.
You did not provide me with enough information to suggest what might be causing this difference. We've made several improvements to SAM since the 2012 version, and one of them could be causing the differences you observe.
Would you mind attaching a copy of your file (saved from the 2012 version of SAM) to your original post above (click Edit and scroll to the bottom of the page to attach the file)?
Best regards,
Paul.