This is still an issue, so I'm reviving this thread.

I made three attempts to book a 24-hour rental via Hertz.com using points for pickup/return at DTW (Detroit Metro airport) next week. The "location is currently not accepting points" error message popped up each time.

Frustrated, I turned to FlyerTalk and found this thread. Sure enough, I called the Hertz Gold desk and VOILA! A friendly phone agent had no problem reserving a car for me using points. It took him about 90 seconds.