seg fault... only on YAST 2? You either have bad ram with convienent timing, bas sectors on your hard drive which part of YAST is sitting on, or possibly a bad install is possible, but less likely.
Try running some tests, I would start with memtest, which came with SuSE, let it run for at least a few hours, best is overnight. If your ram has errors, that is pretty much that. If it passes, then move on to HD test, I personally use ontrack, and a couple others, but the choice is yours.
If both those pass, it may be software side, so it would be time to look into reinstalling I would think. I don't know of a way to just reinstall YAST.