I have a new machine with a Radeon x1600 Pro, 512 megs of ram, and Vue 6 openGL is working as it should.
Lyne, to me it seems it's the new poser import features that are the trouble, since Vue5 runs perfectly in openGL. Checking to import with Poser shader tree and reposing features are very resources intensive. My new machine looks a bit like yours, except that I have an Intel core 2 duo CPU running at 2x  2.13 ghz, and I have no problems, but I do have latencies if I use the new poser import options.