As a quick fix, try this - log in to the admin section of your site and go to /wp-admin/options.php
. You'll find a list of options and their values - search for 'contempo-notifier-cache'. It should contain some XML, including a version number. Copy that text and put this after the line function get_latest_theme_version($interval) {
return "{paste the 'contempo-notifier-cache' value here}";
Hopefully it goes without saying that you'll have to replace everything in quotes with the value in the 'contempo-notifier-cache' options field. Even then, I can't guarantee that'll work, but it looks like it should at least send back the same version number you currently have, hopefully fooling the theme into thinking it's completely up to date.
Meanwhile, find another theme. Even without looking at it I can almost guarantee there are security holes in there.