No problem. Glad I could help.
I had the same problem, and I believe I resolved the problem regardless of permalink structure.
It looks like the standard way to get the current page number of a single post is to use “global $page”. I found this in wp-includes/post-template.php in function wp_link_pages.
So in number-my-post-pages-plugin/numbermypostpages.php if you replace
$cururlarr=explode(“/”,selfURL());
$curpagenum=$cururlarr[count($cururlarr)-1];
with
global $page;
$curpagenum=$page
it should show the right active page number.
