The problems STILL persist, even after applying a bios and video card update also. A few times, a NEW problem has cropped up. The computer will just "freeze" for about 30 seconds, can't move the curser or do ANYTHING, then it will go back to normal.
Since I've fully restored the operating system, I can only assume there is a hardware issue somewhere. If so, this desktop will have started having troubles earlier than any I have owned before... and it's only about 3½ years old!