The new versions of Mint 2.01 and Mint 1.3 should resolve the update available issue.
Clicking the “Update(s) Available” button will dismiss the button until Mint checks for updates again and redirect to the appropriate uptodate page (Mint 2).
Mint 1 has a new Preference, “Ignore available Mint 2 updates”. This means you won’t get the constant nag to update to Mint 2 if you choose not to upgrade but you will still be notified when an update for Mint 1 is available.
There are also a couple additional tweaks to improve support for SSL/https and subdomains.