Another data point:

I experienced this error twice recently, the latest time at a specific hotel in New Zealand. I stayed at 3 different hotels on the trip and saw this problem only at one specific hotel, and only on flyertalk.com. I used FF and did not try other browsers.

My workaround was to use the mobile site m.flyertalk.com, which functioned perfectly. After reaching my next hotel, I switched back to the regular site and have not had the problem recur.