How to force Views (or whole Drupal) to lowercase page paths?
This is untested, but I believe you can use a hook_url_outbound_alter() for this, since I think Views URLs still get run through url() when they get generated:

function MYMODULE_url_outbound_alter(&amp;$path, &amp;$options, $original_path) {
  $path = drupal_strtolower($path);
}


(Updates to address some comments post acceptance.)

This should update URLs that get generated by Views, and will prevent the uppercased ones from getting out into the wild.

Drupal 7 is case-insensitive with regards to inbound URL routing.  However, I am not 100% sure this is always the case with Views arguments being pulled from the URL.  I suspect that the base part of the path w/o the argument is being matched by Drupal as case-insensitive, and the argument is matching case-insensitive because of database collation being case-insensive.