If you want to use HD Cache you'll have to cranck up some values, I dont remember the name right now, I'm not at the computer, but are the three values at the right of the HD Cache settings, the position, normal and the third one.
Put those to 4,70,4 respectively, this will avoid flickering, it's working pretty well for me and I'm doing a complex animation inside a house were practically everything is indirectly lighted.
Cheers.