Only yesterday I complained about not being able to find the RAM buffer sweet spot, and slow HDV renders in 32bit mode (up to 45% of my quad QX6700 resources) when compared to 8bit (or V7) 100% CPU usage.
Well, having 4GB RAM total, I set the buffer for the max allowable size (1022MB) and now it renders with 100% CPU usage under Vista x64, with 32bit on! This doesn't work under XP, so...could it be the code is beeing slowly optimized for a 64bit environment?