My computer and I just don't get along all the time, and my browser refreshed and resent a new thread I had posted a second time on me while I was trying to recover from a lockup. How do I delete the second thread? I closed it... ("DH finally broke his plateau")

Go to the bottom of the duplicate post and click on "edit". The post will come up in a box. A "delete" button comes up on the lower part of the box.

A MOD caught the duplicate and deleted it for you.