I'm assuming the reason that I can no longer open Konsoles, Gnome terminals, or xterms when running 2.6.15 is because pseudoterminals don't work anymore. I'm using gentoo kernels, and I upgraded from 2.6.12-gentoo-r10 to 2.6.15-gentoo-r1. When I upgraded, I copied over the .config, and did a "make oldconfig". I'm guessing something didn't transfer over. No question that I was asked had anything to do with pseudoterminals, and I went through all of the menus in "make menuconfig" and didn't see anything of the sort.
Don't use such things like make oldconfig between kernels that are a couple of versions apart...