6GB DDR2 (2x1) (2x2) different,all - Memtested, for a while, no problems.
So, I got new better cooled case, and new GPU, add 2g of RAM to deal with Premiere no being able to manage 7, yes 7 layers, so mercury hack and all, the video actually stutters more now than with software only. Bar goes from red to yellow but stutters more.
More facts, when I open new tabs on chrome the music stutters too. Vimeo full screen stutters too. Something makes me thing it's all related. Something is wrong but I don't know what.
Recent Windows 7 installation also. Old one didn't stutter on VimeoHD fullscreen, neither.
Performance monitor does not show any interesting spikes when I do either, obviously in premiere rendering CPU is max and RAM almost. Temp is arround 50ºC.
So, I know it is not a perfect machine but it should do all this tasks without any hiccups.