Parameter page=0 gives problem in rules
Having a look through the code of the module, the function that checks if the url parameter exists is this:

/**
 * Rules condition callback.
 *
 * Checks if the specified URL argument is set.
 */
function rules_url_argument_argument_exists($argument) {
  return !empty($_GET[$argument]);
}


This will return false if the argument is 0.  

I think it should really be this:  

/**
 * Rules condition callback.
 *
 * Checks if the specified URL argument is set.
 */
function rules_url_argument_argument_exists($argument) {
  return isset($_GET[$argument]);
}


Might be a good idea to submit an issue (and maybe a patch) in the modules issue queue.
I'm not exactly sure why the function gets the argument argument and doesn't use it
I have never used this module BTW.

EDIT:
There is also if (!empty($_GET[$argument_name])) { on line 71 of the module file that might need changing to isset.