If it makes a difference with open GL on or off it is likey your graphics card and/or driver. First step would be to see if you have latest version.
i updated the last ati drivers and i used a tough ati video card
and it doesn't fix it
can you replicate my issue?
i found some information here http://forums.adobe.com/thread/681729
i googled cs5 opengl on vs off , and i found some benchmarks , i don't know but seems cs5 with opengl OFF is faster, really don't know