I recently acquired a scarily fancy desktop, with an Nvidia GeForce 7950 card. It runs SL so much better except for one issue: tortured cylinders and boxes, once I taper them past .95 or so, are only sporadically visible. They start out visible, but moving them causes them to temporarily (and sometimes permanently) disappear, and selecting them can also cause them to permanently vanish. Changing the camera angle sometimes brings things back into view, but not always, and they usually vanish again when the angle is changed back. While they're not rendered, I can't even select them to edit them. This isn't culling due to distance: I'm zoomed right in. And I've got object detail turned as far up as it will go, just in case. Prims don't seem to vanish if linked to a larger object, though I haven't tested this much.
My old computer, as astoundingly lousy as it was, didn't do this. I've got the latest driver, and I've turned up the rendering quality on the card as much as I can. Does anyone have any suggestions? A large chunk of my SL income comes from jewelry making, which is nearly impossible in this situation.