What, if anything, have you been running in your xterm before it gets
screwed up?  Just top?  What about more, pine, vi, etc?  How about
``clear'', which clears the window and homes the cursor?

Is it possible that some program or other is setting strange stty(1)
settings (what happens if you type ``stty sane'' to restore a saner
handling of the console)?  Or maybe the TERM/TERMCAP environment variables
are getting set to garbage?

Which version of NetBSD are you using?  Maybe a ``uname -a'' output would
help.  (Barring TERM/TERMCAP problems and bizarre stty settings, I
personally haven't seen anything like what you describe---not on 1.3
through 1.4.1)

  "I probably don't know what I'm talking about."  --rkr@rkr.kcnet.com