Backspace key not working in editor

[Vidiot]

Fedora Core 6
Shell being run: zsh

OK, here is the thing that I can't seem to find... as myself, when I log in,
I'm set up to use zsh.  When I edit files with vi, pressing the backspace
key yields the expected results, i.e., the character to the left of the
cursor is deleted.

But, when I "su - zroot" (zroot is the zshell root) it does not work.
Obviously I am not going through the complete login process, so what do I
have to set to get vi to work correctly with the backspace key?

It is extremely frustrating to not have the OS do backspacing correctly.
I'm sure I fixed this with FC2, but the upgrade to FC6 wiped out what I
did and I do not remember what I did, as it was ages ago.

FYI, it is also wrong if I su to root, which defaults to bash.

MB
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