Problem with urxvt + zsh + backspace

I use urxvt in combination with zsh. However since my fresh install of ubuntu 10.04 I have the following problem. If I type backspace the cursor moves to the right (instead of deleting the characters on the left).

Suppose I typed n characters then pressing backspace n-times moves the cursor n- positions to the left, if I type backspace then one more, the cursor doesn't move anymore.

If I type the left arrow, nothing happens, if I type the right arrow afterwards a some character occurs.

mv .zshrc .zshrc.bak
mv .Xdefaults .Xdefaults.bak

didn't help.

urxvt + bash works fine as well as xterm + zsh.

zsh-version: 4.3.11-4ubuntu2.is.3ubuntu1 rxvt-unicode version: 9.09-3

Any idea how to fix this?

(compare: http://askubuntu.com/questions/54145/problem-with-urxvt-zsh-backspace)

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: rxvt-unicode 9.09-3
ProcVersionSignature: Ubuntu 2.6.38-10.46-generic 2.6.38.7
Uname: Linux 2.6.38-10-generic x86_64
Architecture: amd64
Date: Sun Jul 24 11:47:47 2011
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427)
ProcEnviron:
 LANGUAGE=de_DE:en
 PATH=(custom, user)
 LANG=de_DE.UTF-8
 SHELL=/usr/bin/zsh
SourcePackage: rxvt-unicode
UpgradeStatus: No upgrade log present (probably fresh install)