Strange key binding behaviour change

[Ian Petts <ipetts@gmail.com>]

I'm trying to track down a problem that's crept into one of my machines.
It started a month or two ago, possibly after an upgrade. Several other
machines with similar setups are _not_ experiencing this.

zsh seems to have lost many of it's previously defined "deafult" key
bindings; Ctrl-A beginning of line, Ctrl-E end of line etc. I have had
to explicitly add these to my .zshrc now, whereas earlier it "just
worked".

On a probably-related note, I can still recall previous command history
entries with "up-arrow", however the cursor now defaults to being at the
start of the recalled command rather than the end as previously.

Machine is an Ubuntu 10.10 box. I'm not in front of it at the moment, so
can't give the exact zsh version, but it is the current/default version
shipped with the distro.

I have been trying to recall/find the "start zsh without any startup
files" option in order to start debugging, but so far without success.

Can someone please assist?

Thanks,
Ian.