Keep getting 'upgrade to 6.4' alert under status

I've already done some upgrades on my local machine (localhost) but this time I keep having problems. The last problem I'm left with: under status report I find:

VERSION INFO:
Drupal 6.4

CORE UPDATE STATUS
Drupal core update status Not secure! (version 6.4 available)

What's up? I ran update.php, cleared the cache (even though no caching is enabled), logged out/logged in, restarted webbrowser. I've run out of options and therefore am posting here. Thanks for any input.

Cheers,
John