[jQuery] $() and Object doens't support error

Hi,
Following some tutorials to include field validation in a WordPress
form.
When I have the following in the js file for my form, I get the
"Object doesn't support..." error.
$().ready(function() {...
If I change it to:
jQuery().ready(function() {...
then the code works as expected. I'm using WordPress version 2.8.4
which includes jQuery version 1.3.2
Any ideas what I'm doing wrong?
Thanks