How to backspace in isearch-forward-regexp

[KARR, DAVID (ATTCINW)]

After installing GNU Emacs on some new boxes recently, I finally
realized one thing that is behaving differently than what I'm used to.

When I'm using isearch-forward-regexp, I can type letter by letter, and
it will update the first match found.  I used to be able to hit
backspace while typing to remove the last character entered in the
search string, in case I made a mistake entering the string.

Now, when I hit backspace, it exits isearch-forward-regexp and sends the
backspace directly to the buffer I was searching in, usually deleting
the previous character at the end of the last match.

I have a feeling this must have something to do with the binding of the
backspace key in Cygwin.

I'm using Emacs 23.0.92.1 on Cygwin 1.5.