Strange behavior when navigating terminal history.

When I look through my bash history (by pressing up), occasionally the first 3 or 4 characters of a command will stay and push everything else forward.
For example, suppose my last few commands were:

vi .bashrc
ls | grep D
cal

And then I was trying to edit .bashrc again. After hitting up three times my prompt would say:

$ ls |vi.bashrc

The command would still work as intended but seeing this is very strange and often confusing at first. I searched around and couldn't really find anyone else reporting this issue and was at least wondering if anyone knew how this could happen. I have a modified prompt, if that could cause it. From my .bashrc file:

export PS1="\e[36;40m\A \w\n$ \e[0m"

So it looks something like:

military-time pwd
$

Any explanation (even if in lieu of a fix) would be appreciated. As I said, it's doesn't really impede functionality, it's just odd. Thanks in advance.

 

Also, I'm pretty sure (although not certain) that this behavior has been present since before I upgraded from Leopard to Snow Leopard on my MBP; in case that might be a factor.

 

After a searching around more I finally found a solution.

http://stackoverflow.com/questions/105349/bash-prompt-in-os-x-terminal-broken

I need to put \[ and \] before and after (respectively) each non-printing sequence.

My prompt is now (it has undergone other changes):
export PS1="\[\e[36m\]\u \w > \[\e[0m\]"