I'm using version 1.3.1 of Wp Updates Notifier and it's unfortunately not sending out the e-mails. The test e-mails are sent without an issue.
After reviewing the forums, I tried installing the cron view plugin to see if it's listed to run and if so when. I have the plugin configured to check for theme and plugin updates hourly. The cron view provides the below information:
Jul 27, 2012 @ 17:13 (1343409207) Twice Daily wp_version_check
Jul 27, 2012 @ 17:13 (1343409207) Twice Daily wp_update_plugins
Jul 27, 2012 @ 17:13 (1343409207) Twice Daily wp_update_themes
Jul 27, 2012 @ 18:39 (1343414385) Once Hourly sc_wpun_update_check
Shouldn't all four of these settings display "Hourly"? 'sc_wpun_update_check' is the only hook which changes when I change the scheduled time.