Suffered same problem with new version too.
Did the same as suggested, knocked sound down to 3/4, reduced textures to 128 instead of default 256. Stopped preloading all into RAM.
Still suffered, then sussed what it was on mine.
My GFX card is o/c'd so the Optest enhancements were pushing mine beyond its limits causing the freezes.
Reduced my o/c settings a touch and all is well.
If on an Nvidia card Skuzzy advised changing driver to 61.77 altho if I remember yours is an ATI isn't it?
Smiggy.