I turned off the 3D desktop (Xgl) and, strangely enough, that fixed the problem with the selection box. It wasn't very stable with 3D applications, anyways.
Umm, false alarm. For some reason, it did work after I turned off the 3D desktop, but now I am seeing the problem again. Maybe it worked because I had just rebooted or something. Anyways, Xgl is not the cause of the problem, it is something else SUSE related. I did download a bunch of updates the other day, and I don't remember seeing the problem before then, so possibly one of the updates triggered the problem, or that's another red herring. Continue with your 3D desktops, just don't try to run OpenGL things full screen, or if you do, make sure to save everything in case X crashes.