Yeah, I like to throw up something about anything I break and then is later fixed (not necessarily by me...), just in case anyone else ever runs across the same problems. Maybe I just get this strange twitch, but who knows if somebody could find it useful sometime. Stranger things have happened.
So, a few days ago after I booted up my Windoze partition to make sure that nothing was breaking, update a few things, and do a few minor things. Of course, when I booted back into Debian (Murphy's law?), all hell broke loose. All of the sudden gnome display manager started repeatedly crashing/exiting, until it was stopped with a warning message after about six quits in less than two minutes (I can't quite remember the exact details/message). Strangely, XDM did not have the same problem.
It turns out that it was something in my locally (non-packaged) truetype fonts (using xfs). I don't know what exactly was causing the problem, but removing them all apparently worked. Didn't actually fix the problem myself. <g> They needed weeding-through, at any rate. Half of them I never even used. I'll eventually re-install the ones I used often, but don't really have the time to do so one by one at the moment.