When I play nethack on konsole and move some steps, the characters start looking weird. It is like the characters don't disappear even if it has moved away from it's spot. Take a look at this and see what I mean:
http://pastebin.com/658068
In rxvt, I get almost the same kind of problems but some weird marks too.
http://pastebin.com/658087
I don't get any problems in aterm (0.4.2), Eterm (0.9.3) or tty. I use Slackware-current, with the most recent packages.
What might be causing this?