I did something similar recently.  I interviewed for a Accounting job in June 2004, was offered and accepted the position.  However, I chickened out, and decided to stay with my then current employer. (It was a bad decision. That' s the job I finally quit in Dec. 2005)  Flash forward to January 2007.  I answered a blind ad, and it turns out to be the same position with the same employer I accepted, then reneged on.

The owner/CEO, however, didn' t recognize me. (In all fairness, I had two interviews the first time, and only shook hands with him.  I actually interviewed with his former CFO & another Exec, and the CFO is the one who hired me.) We interviewed, and I let them know I regretted turning down the position previously, and wanted to work for them.  It seems they hired someone for the job after me, and they only stayed a few months.  The Controller (who, by the way, did remember meeting me the first time) has been handling everything since.  Well, I guess the second time wasn' t a charm for me, cause I never heard from him again, even after contacting him about his decision.

If they did recognize your name from last time, the fact that they set up another interview means they were impressed with you six months ago.  Maybe you were their second choice then. And, I think it' s perfectly acceptable to ask what happened to the person they hired.

There seems to be a lot of this going around, lately. I had interviews at two companies since last November that had ignored my first resume/cover letter sent.  About two months later, both positions opened up again. I resent to both, and got interviews at both.  One company offered me a position, which I turned down.  In both cases, the Accounting Managers they hired had not worked out.  So, you just never know.

Good luck on your interview!!!