came here just to post the same question. feature doesn't work for me too.
Premove problem

Premoves need to be re-enabled if you want to use them now sorry.
Click on the link below, enable your premoves, remember to save settings, then refresh live chess page (not during a game)
http://www.chess.com/home/livechess_settings.html
Hey guys,
I just played a couple of blitz games and to my surprise I found that I couldn't make premoves anymore. I'm wondering, has that feature been disabled permanently, or is it some temporary problem, or is it something on my end???
Thanks!!!